@Austriacus
Sure, he and his friend atleast showed eachother or told eachother their skill levels, but there wasn't any mention of stats in this chapter between them other than maybe the friend commenting on the size of his field, which implies good physical capabilities.
And yes, even if he knows all the stats before the OP happens, he doesn't know how they compare to other classes in the kingdom.
As for when he became OP ? He knows he's OP, but he still didn't know what to compare it to, because he has nothing to compare it to before arriving at the city, finding out the 'scale' or alternatively the dragon or kidnapper.
Let's see... as a comparison, he went from being able to lift 10 kg, which he knows his neighbours and friends can do , or if not, then not far from to being able to lift 1000 kg, which he knows they can't do, but he has no knowledge as to whether anyone not from their region can do it.