quick question about sonic acceleration

[Rock Steady]

The description for the sonic acceleration says it increases sonic blow's success rate by 50%. Does that mean you gain half of the hit you initially have, +50 to hit, or something completely different in terms of formula or whatever? I've always been abit confused about it and i wanted to see if anyone knew. Thanks !

[crash]

Half of the hit you already have. Example: you have 50% hit rate on a monster (you've got 150 HIT, they require 200), SA will make it 75% (or 175 HIT) when you use Sonic Blow.