For volumes is that suppose to be for the number of tankoubon release or how many tankoubon that can possibly be made?

Every dead body that is not exterminated becomes one of them. It gets up and kills! The people it kills get up and kill!

the amount out in japan

If you know the amount planned and you know it's correct, then use that number. If it's an ongoing thing with no real end that you can see right now (like Naruto...), then list either the current volume released in Japan, or the volume # that the latest mag release will be in (if you know it)

A just ruler amongst tyrants