For milling moves, you must enable the C-axis and orient the C-axis in both of these formats.
Here is an example for the Acramatic 850 TC:
<IF><MILLING><THEN> {N<SEQ>}M21<EOB> {N<SEQ>}S<SPEED><SPINDLE> <EOB> {N<SEQ>}C<ROT1-WIND><EOB> <ENDIF>