CTS/XDF games are ignored if you don't reach the finish checkpoint
You can play well for the full duration of a game and make significant progress towards completing a map, but if you can't reach the final checkpoint, xonstat ignores the game and the play time. For newbies, and experienced players who prefer the hardest maps, this means not counting most of their cts play time.
This also makes the server appear inactive even though players were playing.
Also, if you are spectating a newer player and trying to help with their technique, this should count as game time.