from around the net:
What's the shortcut to nudge rotation in AE 1%?
You might think a modifyer key and the old shortcut numpad +/- would work. Oddly, you won't get the result you want that way, but you don't have to resort to null layers and expression decimal mulipliers. AE's own DaveS has the clarification..."for any property click on the hot-text value (underlined) in the Timeline or Effect Controls panel, then hit:
Up/down arrow to increment/decrement by 1
cmd-up/down arrow to go by 0.1
shift-up/down arrow to go by 10
On windows, use ctrl instead of cmd.
For some effect properties with limited ranges, the default nudge increment may be different than 1, but adding cmd or shift will always decrease or increase the increment by a factor of 10. For nudging Clone Time on clone strokes, default is one frame, adding shift is one second."