Top end rebuild questions

[TGM_OFFROAD]

Hello All, I am in the process of replacing the top end of my 2018 XC300 and since it is my first time on this bike and first 2 stroke in a long time I figured I will have at least a few questions for the internet gods.

First question, when cleaning my cylinder I scraped all gasket material from the head including the right side power valve gasket. In doing so the gasket came off in pieces. This did not concern me because I assumed it came in the gasket kit I ordered. Well the gasket kit does have a right side powervalve cover gasket but it is paper thin while the one I cleaned off was about 4-5mm thick. I see on the parts diagram that there is a 6mm gasket shown. The question is why is this such a thick gasket and if it is supposed to be a thick gasket why would a thin one be included in the OEM gasket kit.