eh I think what he's doing is multiplying by 10, not sure tho, I'm really not good with these kinds of languages lol, how am I supposed to know what fold(-mate, mate) means if it's in one of those thousands of other source files
So I'm not sure what Stockfish is outputting exactly, but I'm sure like all other modern engines it determines the depth in Ply until checkmate is reached. so if mate_depth_mov_ans < mate_depth_mov_played then bitch in the comments. :D
Something like that.