ARLINGTON, Va. >> Nineteen rows down and 20 to the right. That’s the math Mimi Robinson wanted to know: the distance between her father and Capt. Humayun Khan at Arlington National Cemetery.

Like many Americans, she was moved when Khan’s father testified to his son’s values and sacrifice at the Democratic National Convention in July. So, a few days ago, she walked the neatly ordered grounds from the gravesite of her father, a member of the Coast Guard who died in 2014, to the marker for Khan.

At the foot of the captain’s grave stone, with its Islamic crescent and Purple Heart inscription, she left a handwritten note on a sheet of loose-leaf paper.

“I’ve been thinking about the ways politics and bureaucracy have tainted my love for this country,” she wrote. “But seeing your parents, learning about you — has shown and reminded me of the dignity, love and blessings stitched into the diverse fabric of the United States.”

Since late July, thousands of people — veterans, relatives of fallen soldiers, even those with no connection to the cemetery — have made their way to Khan’s grave, deep inside the cemetery, to bear witness and offer words of support.

“We try to count the messages” left behind, Khan’s father, Khizr, said in an interview Friday. “We have exhausted number 4,000 and counted on.”

Humayun Khan would have turned 40 on Friday. Khizr Khan and his wife, Ghazala, were too busy that day to visit his grave, but on Saturday, a day before the 15th anniversary of the Sept. 11 attacks, they made the more than two-hour drive from their home in Charlottesville, Va., as they had countless other times.

The site — Section 60, Grave 7986 — has become so frequently visited that tour guides and other staff members have memorized the grave number so they can offer directions. It has emerged as a kind of organic meeting point, where lives intersect and people like Robinson come to do that math of proximity and sacrifice, and to make a statement about what Khan’s story adds up to.

“He was a person that put a face to everything good about minority groups in America,” Robinson said in an interview. “He’s what we all value in this country really deep down. It’s him and it’s other soldiers who don’t have the spotlight like he has right now.”

Khizr Khan, who in his speech at the Democratic National Convention delivered a blistering denunciation of Donald Trump, the Republican presidential nominee, and whose family Trump later belittled, said the address had offered a reminder that “certain values are worth fighting for.”

“Those values are and remain our values through Capt. Humayun Khan’s values: care for others and the good of the nation,” he added.

Charles Cowherd of Alexandria, Va., whose twin brother, an Army lieutenant, rests in a grave three plots from Humayun Khan’s, has been visiting Section 60 since 2004, when his brother was killed in Iraq. Khan died just weeks later, also in Iraq, in a suicide bombing in June at his base.

That section of the cemetery contains the remains of many other service members who have died in the wars in Afghanistan and Iraq. Lately, Cowherd said, he has noticed a difference among the mourners there.

“The composition was a little bit different going to that grave,” he said. “It touched a segment of people that wouldn’t be going there otherwise.”

Some, he said, are offering a rebuttal to Trump’s denigration of the Khan family. Trump, for example, played on religious stereotypes by suggesting that Khizr Khan had not allowed his wife to speak at the convention.

“I think the people going there was a way of drawing distinction and saying that we as Americans support this family and support this fallen soldier, in a way, more” because of Trump’s comments, he said.

The letters collected from the gravesite end up piled in boxes on the dining room table at the Khans’ home. Slowly, Khizr Khan said, he and his wife are working through them. They read each note and write to thank those who have left return addresses.

The stream of visitors to the gravesite has subsided somewhat as fall has approached and as Khizr Khan and his wife have returned to something closer to normal life. After a crush of television appearances and media interviews after the convention, they have largely stayed off the air in recent weeks.

They now have help from a public relations specialist, Stephanie Cutter, a former aide to President Barack Obama. And Khizr Khan said he had tried to cap the number of speaking invitations he had accepted.

But the letters are still coming at Grave 7986, new ones seemingly every day.

Jennifer Lynch, a spokeswoman for the cemetery, said the grounds crew removed objects left at gravestones when they became “unsightly.” Along with letters, visitors to Humayun Khan’s gravesite have left stones and American flags, photographs and laminated prayers, and flowers of almost every color. The Khans have employed friends who live in the area to make frequent stops to collect the items, for later delivery.

When the Khans visit the cemetery, the ritual is different now. Staff members do not question who Khizr Khan is when he forgets his entry pass to drive in. Visitors approach him to introduce themselves. The gravesite, too, is no longer the family’s alone.

“If we are standing there at his gravesite, of course people begin to gather, and I will greet them and shake their hand, and they often ask to take a picture,” Khizr Khan said. “And then I’ll quietly move back just to take a picture myself.”