Wow, adding the 0.5 works flawlessly. So how does litestep round off? I'm guessing it's simply a truncation (floor) since adding the 0.5 seems to fix the problem.

Edit: Hmm, although the problem is fixed, I'm messing around with the Winamp volume controls and comparing the volume display to the [volume], it seems winamp is also flooring output in the display, but it doesn't seem to be flooring the volume change through the !Amp_SetVolume bang?

Eitherway, I found that adding the !Labelmove bang with a 0.5 seems to create a closer correlation between the [volume] and winamp's volume that adding 0.5 to both the !Labelmove and !Amp_SetVolume.