[Al Skierkiewicz]

18. All mechanical fasteners (nuts,bolts,screws,etc.) of any length, any thread type, up to 0.375” (0.9525cm) diameter. The intent of this rule is to allow teams to use fasteners from any supplier that are substantially the same as TETRIX fasteners. Compatible fasteners are characterized by using the same thread characteristics as TETRIX fasteners. For example, an acceptable substitute for the TETRIX 6-32 thread,1/2" length socket head cap screw is a 6‐32 thread, 3/4" length, button head cap screw purchased at a local hardware store.
Emphasis mine.

I do not remember any sheet metal screws in the Tetrix kit.

The receipt should be acceptable proof, if needed. Most often a comparison with other Tetrix parts on the robot is sufficient to determine thickness.