I thought the ones on field level were always 16oz whereas going into one of the bar areas would sell you 20oz for like $1 more. And I did the same on Thursday. Chasing Citra was my "walking around" beer as I was checking out all of the new stuff.
Don't recall them being 20oz last year but could be wrong... I didn't drink anything other than Speedway at the park in 2017!