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