IE 66ers

So this is a weird question but on Wednesday the 10th the 66ers are playing the Modesto Nuts and the theme game is nothing day where the tickets are apparently free and you bring in your own food. When I tried to secure the tickets for the game online they tried to charge me the standard ticket fee. Does anyone know if you just pretty much show up to the stadium and they let you in or do I gotta RSVP because I’m very confused and I might just buy the tickets to 2$ tuesdays if I cant figure it out lol