10, 2 50, 2 driving me nuts!!!

add_login_logout_to_menu', 50, 2 );

add_login_logout_to_menu', 10, 2 );

I’ve searched the web & Codex trying to make sense of what these numbers represent.

Does anyone one know what’s the difference between 50 vs. 10?

Nobody explains this. Is this some sort of a mystery that never gets explained?

lol, but seriously, I just want to know.