Replying to Need some binder help fast

i got an edge on my old ski fixed a whilel ago and theres suposed to be a big snow storm tomarow and i was going to hit some urbans, so i got the skis out and the guy who fixed my edge moved the binding so its a lil too big to fit my boot, i got some p12 jibs about 2 years old, how do i make the binding a little smaller? i tried to unscrew this screw under the heel and it made it loose but i couldnt push it to make it a little smaller, should i just push harder or am i doing it wrong?