To override Automatic Spacing, use the Ctrl+0 shortcut to toggle automatic spacing on and off.
For example, to type 1.A, use Ctrl+0 before and after the period. (Without toggling automatic spacing, the result would be 1. A with spacing after the period.)
You can inhibit spacing after an expansion by adding a trailing underscore ("_") at the end of the Long form of your glossary entry.
You can also turn off automatic spacing selectively using the Automatic Spacing Options Dialog. For example, you can completely override automatic spacing after a comma by specifying the value zero for commas.
A backspace always cancels automatic spacing. Thus, you can also type 1.A by backspacing the spacing inserted after the period.
See also: Overriding
both Automatic Spacing and Automatic Capitalization