No clue so far, got 17735, but the second playthrough is different and i didn't get a number.
wait, some numbers appear in the pause menu. first playground i got 144. after i xxx one time it turned 216. it might be the final xxx score! It must be. i guess the only ones one can miss are the ones in both mazes. As Lu says in the middle of the game, she might add it to the game as points to collect. I wondered if they will appear anywhere.