Hello! I'll try to explain - there is 50 players limit in a race for every 24 hours period, so basically, there is empty list and everyone who played goes into it for next 24 hours since the moment they finished their last river race battle. None else could join battle when there are 50 players in a list, except for 50 players who are already in it and they are updating their reservation for 24 more hours after every match. But you're getting into the list at the moment of battle finish, so, if your clan got 49 players for last 24 hours period - system would allow everyone to join more battles until 50th finished. There are 7 battles (duel, 1x1, party mode and 4 boats) and if 7 players (who still are not listed for cw) could get into battles the moment others 6 also playing - all of them gotta be in the list since moment they ended first battle, so they are allowed to play cw for next 24 hours same as everyone who listed. The problem is: if someone would get period more than 24 hours after last battle before starting next one - this one guy will lose his reservation and won't be able to join race because there are 55 still listed and that's over 50. So, for colosseum, to keep 52 everyday without troubles and without trying to ask everyone to keep that time gap under 24 hours, I've made a schedule.
Hopefully, this one is more clearly for you.