Each move has it's own PP cap, dependent on the base PP it has. each use of a PP Up raises the moves cap by one fifth of the moves base PP. So, a PP Up would raise a 5-point moves by one, a 10-point move by 2, 15-point move by 3 and so on. The maximum amount of extra PP a move can have is three-fifths the base. So, a 5-point move can have 8 (5+3), a 10-point move can have 16 (10+6), etc. In that vein, a PP Max raises PP to the cap, and therefore is potentially three times as effective as a PP Up.
/game mechanics