Water lost to steam heavily depends on style of cooking, or more precisely, in a covered pot, is mostly a linear function of the excess heat beyond that required to bring contents to boiling temperature (steam re-condensation on the lid/sides provides a slight buffer) + a bit lost to empty space in the pot (when opening etc).

Some stoves are hard to regulate so the food is just barely boiling, so it can be hard not to notably lose water.

From experience, the boiling of water in itself is mostly meaningless when cooking, unless you want food extra shredded. You can happily cook at 90℃ or 80℃ if you want, but it will take longer.

Note if cooking risky food: beware of required time at a given temperature to kill pathogens, not forgetting heat transfer takes time especially in solid chunks.