[Wish]

power gives +20 strength and +50 hp and + 5 to attack, defense, and precision. (stats)

subsequent wishes have half the returns: 25hp/10str/ 2.5 stats
you may be thinking 2.5 stats? whats that mean?

that means on the second wish for power you get +2 to atk/def/prec. on the third you get +3 each, on the fourth you get +2... etc. (the .5 is rounded down for showing stats, but exists to be added to subsequent wishes)

"stronger", "strength", "hit points", etc. are the exact same effect. (stronger gives hp and stats too, hit points gives strength and stats)