20. For the purposes of this Act, a detainee shall be taken to be complying
with an order for periodic detention if he or she serves his or her sentence
in accordance with an order of the Director made under
section 15, 16 or 17 in respect of the detainee and while the
detainee complies with such an order that is inconsistent with a provision of
an earlier order of the court or the Director in respect of the detainee, the
earlier order shall, to the extent of the inconsistency, cease to have force
or effect.