AM_SET_PREFIX_REL_SIZE sets the default size for dimension
prefixes relative to the size of the main dimension value.
----->(AM_SET_PREFIX_REL_SIZE)------|size|------>
This command has no options. Enter a relative size for dimension prefixes.
Use this action to set a new size for subsequently-created
dimension prefixes, relative to the size of the main
dimension value.
AM_SET_UV_ABS_SIZE terminate action,
AM_SET_PREFIX_ABS_SIZE terminate action