From posts here and other boards, most people have found that you need a minimum of 125 ml of stock Xtol for the standard times. Even 100 ml is too little.(posted 8687 days ago)Now with extended times, I can see from their data that 70 ml should be fine.
The problem is, Kodak seems to contradict themselves in the data sheet. At one point the explicitly say that you need 100 ml of stock per roll, then they say that from 1-5 rolls per liter you develop for normal time, but for 6-10 you need to increase the time. Without further explaination, that seems to be contradictory.
They need to STATE that one is for one shot use and the other is for reuse/mixing.
But for me, unless I want to do some testing, I will use 125 ml of stock per roll at whatever dilution.