[john.gersh]

I'm afraid that my behavior analysis was all wrong. I generalized too much from the units in your example.

I looked some more and found that the real behavior (snap on, 100% zoom) is:

• Arrow moves one minor grid division.
• Shift-arrow moves one point.

Zoom affects shift-arrow in the same way as before.

I still can't figure out where your numbers come from.

One slightly-confusing UI feature: In the grid settings, the fields are Major Grid Spacing and Minor Grid Steps. In other words, the first is the length of a major grid step. The second is the number of minor steps in a major one, not the minor step length.