I'm assuming by igt 23, you have a G-23 cabinet either using a 2.5 or 3.0 avp box, either way if you open the C door, there should be 2 usb ports. Put your 7 key in one of the two and it should bring you to the elevated security main menu. Go to Setup -> Game -> Enable/Disable -> click on slots, then the game you want to change. -> I think the top option on the right side of the screen will bring you to the denom / hold percentage, then you just switch the percentage and save.
If it's an ascent box, the screen after you hit enable / disable will look different, but it should be pretty easy to find from there. I know this is pretty late, but hope it helps
