With less than 2 grams of microbes and about 15 lbs of cyanuric acid being converted, that means that each microbe consumes thousands of times its weight in cyanuric acid. That seems like quite a lot.
The organisms are used as a delivery vehicle for the creation of the necessary enzyme chemistry only. The enzymes are catalysts and as such can perform multiple reactions without being used (unlike chemicals). So the microbes produce the enzymes and the enzymes then break down the CYA and ultimately its byproducts such as ammonia etc.