NEW YORK (AP) — “Gran Turismo: Based on a True Story” and “Barbie” are in a dead heat for the box-office crown, with the video game adaptation just edging Greta Gerwig’s pop sensation, according to studio estimates Sunday.

Sony Pictures reported that “Gran Turismo” opened with $17.3 million over the weekend, while Warner Bros. estimated that “Barbie,” in its sixth week of release, took in $17.1 million. Those totals could change when final ticket sales are counted Monday.

Due to a few wrinkles, it’s all but certain that “Barbie” sold more tickets than any other movie Friday through Sunday, even if “Gran Turismo” is claiming the checker flag.

One reason: It was an usual weekend in multiplexes. US movie theatres held the second annual National Cinema Day on Sunday, with $4 tickets to all films and showtimes at nearly all of the country’s theatres.

“Barbie” was expected to be easily the top draw during the discounted day, with a particular boost coming from repeat viewings. With a domestic total of $594.8 million in ticket sales, “Barbie” has passed “The Super Mario Bros. Movie” ($574 million) to become the year’s biggest domestic hit. With $1.34 billion worldwide, “Barbie” will also soon surpass the leading $1.35 million worldwide tally of “Mario.”

National Cinema Day is meant to lure moviegoers to theatres during a typically slow period — and recoup the lost ticket revenue by selling a lot of popcorn. Last year’s event drew 8.1 million moviegoers, making it the busiest day of the year in theatres. Warner Bros. estimated that “Barbie” would gross $7.8 million on Sunday, which would mean almost 2 million people saw the film that day.

So what was the top movie in theatres this weekend?

“Barbie,” says Jeff Goldstein, distribution chief for Warner Bros. “Without any question.”

Though “Barbie” is the weekend’s top draw, “Gran Turismo” has a slight — and somewhat debatable — edge in gross earnings. In its weekend totals for “Gran Turismo,” Sony is also factoring in a hefty $3.9 million from preview screenings held before Thursday, along with $1.4 million in Thursday previews. Such accounting, while common practice for Hollywood, has stretched the definition of an opening “weekend.”

“We’ve made a big issue of it only because ‘Barbie’ has had incredible holds,” says Goldstein. “To take away the number one, which would make it five weekends at number one since it opened, kind of doesn’t feel right for the ‘Barbie’ filmmakers who really deserve the accolades.”

Sony executives declined to comment.

Either way, it’s a so-so start for “Gran Turismo,” which cost about $60 million to make. But the film, about a young man whose love of the PlayStation video game helps turn him into a real-life racer, has gone over well with audiences. Moviegoers gave the Neill Blomkamp-directed movie an “A” CinemaScore.

The ongoing strike by actors and screenwriters has taken away the studios’ ability to promote films with their casts. To help spread the word on “Gran Turismo,” Sony held several weeks of preview screenings and fan events.

Last week’s top film, the DC Comics release “Blue Beetle,” slid to third place in its second week, with $12.8 million. The Warner Bros. film has made $46.3 million in two weeks, making it another misfire for DC.