To my knowledge, and I could be wrong, there is no test to tell you. But it’s quite a bit. Back in my CKD days, the protocol was to eat an EXTRA days worth of calories in carbs over a 36 hour period. That’s extra, not a substitution of carbs for your daily caloric requirements. Full recompensation like that is really for those training and following a CKD.
The reality is that you can easily substitute some carbs for fat over a meal, day, or even longer and come no where near filling up your glycogen. It really takes a chronic pattern. That’s why people can take an occasional break, and as long as you don’t intentionally overeat, never get to the point of overcompensation. It’s all about considering VLCHF to be your norm, and carbs to be a temporary exception. All this really only applies once you’re adapted, it’s not a good idea until that time.
Last Fall I got to the point when I was never hungry, a few weeks of simple caloric substitution restored things for me. That and forcing myself to eat some limited carbs on the Weekends.
If you could remember how much weight you dropped at first when you became lipolytic would be a good indicator. For me, since I recompensated reqularily, I know I carry (or used to) around 14 pounds of glycogen. I can actually flux much more water weight if I eat salty foods at the same time.