Munching,to satisfy your curiosity in this regard I really would recommend that you ask the girls concerned what theymean by sub games.
Reason : because they'll almost certainly all mean different things - from the girls who have ticked that box because they read 'Fifty Shades' on holiday and think it makes them sound more kinky and interesting, to those who will crawl about on all fours at your command ,to those who will kneel in the bath with their mouths open having begged you to use them as a toilet.