The civilopedia was written for Fire version .20. In that version, the Armageddon counter had a fixed minimum of 0 and maximum of 100. This led to it rising far too quickly on Huge maps or if there were too many civs, so it was change to display as a rounded percent of the true maximum counter value, which varies based on map size and number of players. The Hallowing of the Elohim/ The Elegy of the Sheaim lower/raise the AC by the number 5, not by 5 percent. The true maximum value of the counter on you map might be about 250 instead of 100. I'll assume that the map size and number of players was not the same every time you built the ritual.
Thank you for your explanation. To answer your assumptions:
1. I always play on a huge Fantasy Realm map. That never changes.
2. I always start with the default number of AI civs - it is 9 or 10. Yes, some are often eliminated by the time I get to build the ritual, so this might be a variable.
I wish I could say this made it clearer, but, truth is, I am more confused now than I was before.
I will check the wiki to see if it will help. As I said, with poor online access, I am, I guess, too dependent on the civlopedia for things.
Thanks again for taking the time to explain.