Looks like the transmission drain bolt. Probably not your culprit since it has tranny fluid, not oil
Being the lowest point it probably dripped from something down to there and from there to the garage. That's an awful small amount of oil (quarter size) but some things to check:
Clutch slave cylinder
Valve cover gaskets
Road Draft tube (very hard and vengeful iron tube coming out of the back and running down the back of the motor - don't bang your head on it)
Oil filter