My memory is fuzzy (used to do sheet metal repair for L3 and Boeing), but I'm pretty sure the FAA requires nearly everything to be "American". This means pilots must speak English and all aircraft hardware is of the AN (army-navy) or NAS (National Aerospace Standard) standard.
Hardware is always in English units (inches). In this case, the #8 screw (5/32") was used in place of a #10 (3/16") screw. Side by side, the size difference is obvious. Trying to judge the screw size by looking at the hole is not so obvious and a #8 screw will sort of cross-thread into a #10 hole because aircraft female threads are "interference fit" by (at least) about .001" so screws and bolts won't vibrate loose. I've made the mistake before but if you are paying attention, you'll know you got the wrong screw just by how sloppy it goes into the hole. That and #8 screws are only used on mostly non-critical stuff. If you were to take every screw,rivet, and bolt on a plane, 90% would probably be 3/16" in diameter.
Hardware is always in English units (inches). In this case, the #8 screw (5/32") was used in place of a #10 (3/16") screw. Side by side, the size difference is obvious. Trying to judge the screw size by looking at the hole is not so obvious and a #8 screw will sort of cross-thread into a #10 hole because aircraft female threads are "interference fit" by (at least) about .001" so screws and bolts won't vibrate loose. I've made the mistake before but if you are paying attention, you'll know you got the wrong screw just by how sloppy it goes into the hole. That and #8 screws are only used on mostly non-critical stuff. If you were to take every screw,rivet, and bolt on a plane, 90% would probably be 3/16" in diameter.