How much water in the tank? eg. Korky valve

I'm getting ready to install some Toto Ultramaxs. Since these are low flow toilets and the purpose it to conserve water, I wanted to make sure I made the correct adjustments. How much water do we actually allow in the tank portion of the toilet? From my unlimited experience, when I used to replace these valves, I could fill the water almost to the top until it fell threw the "big tube". I want to make sure I have the correct height. Is there one? Thanks

Normally, the fill valve is already installed and adjusted on Totos. If not, or it is not adjusted properly, the water should come up to the mark on the tank. Note, when it becomes necessary to replace the flapper valve, try to get an exact replacement - some of the aftermarket ones either close early or late, compromising the flush or wasting water.

The Toto Ultramax and the Toto Drake come adjusted from the factory.

Of the thousands I've sold, I've never bothered to change the factory setting.