its correct, damage scaling.. the more hits you do, the more the damage gets lowered as the combo progresses. B+2>B+2>F+4,2,grab is very chunky. also if you freeze someone, that lowers the damage even more severely. this is why almost none of my combos in the list i put up has a freeze effect incorporated, you actually end up with less damage.
also your using grandmaster, wich is lower damage then cryomancer wich is what this thread is for. EX hammer and F+4,2,grab are both large sources of cryomancer damage abilities
edit: you can of course get 38% if you do a jump in