Say if the position of an image was '960.0, 540.0' and I typed '+20' on the X value, the position would become '980.0, 540.0'. However if I wanted the position to become '940.0, 540.0' by typing '-20' on the X value, the position would become '-20, 540'.
You probably had the x value highlighted.... in which case when you type "-20" the layer moves to the -20 x position. If you DON'T have the value highlighted, it works as expected.
And if you're double-dog sure after having replicated the behavior precisely that AE's displaying weird behavior, this is the first time I've ever heard of it happening and we;ll need a lot more information to diagnose what's going on.
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA