This may be a stupid question, but is there a maximum alliance prestige value that hasn't been told to the players? The reason I ask is that my alliance just cleared 5 x Map 6 and we noticed that the point total applied to our day 5 clear was only 700k higher than our total on day 4. This seems odd given that our prestige was increased by 921 from day 4 to 5. Maybe I just don't know how the calculations are done? Does anyone have any insight on this?
Here are some screenshots showing what I'm talking about:
Day 1 - 2:

Day 3 - 4:

Day 5 (today):

Any help or insight that anyone could provide would be greatly appreciated.