9 Kerning and Tracking Increments
Speaking of kerning and tracking, InDesign’s kerning and tracking is based upon a 1000 em unit square, and you can adjust the spacing between characters in increments as small as 1/1000 of an em (an em is relative to the point size of the type: for example, with 24-point type, an em is 24 points). On a cautionary note, I recommend that you change the factory default for the kerning and tracking increment from 20 to no more than 5. This determines how much space is removed (or added) when you use the Option/Alt+left arrow/right arrow keyboard shortcut to apply tracking or kerning.
Figure 9 Reduce the default kerning amount (also affects tracking) to 5 or lower for finer adjustments when kerning or tracking using keyboard shortcuts.