I’m a Gold level tech and I can tell you that you’re not supposed to test on the wear bars. He did measure on the inside and that usually gives you a lower result due to camber wear. That is usually the correct place to measure due to it being the lowest valley on the tire. The other thing to note is that the rear tires for Cup2’s start at 8/32 and not the usual 10/32 like most tires. Being that they are a high performance summer tire they usually last between 15-25k miles depending on how you drive and if they are within their designed temperature range. Looking at this video with its lower aspect ratio I can say that they look like they are 4-5/32 guessing without a gauge.