I haven't heard any numbers, but there were a lot of people there...the main grandstands along the front stretch seemed pretty full, the grandstands on turn 4 and 3 looked maybe 1/2 full from what I could see. After the race, It took about an hour to get out of the parking lot and an hour to get back out to the freeway. Last year, though, being the 100th anniversary, most likely had a bigger turnout..was estimated then at 400k IIRC...and the heat this year didn't help. I was there Saturday also to visit the museum and vendors, it was pretty crowded then as well.