No difference, percentage = numbers unless you use text, if so copy an empty
cell, select the percentage and do edit>paste special and add
That will convert it as well, otherwise format as percentage

There is no reason why you should not be able to use MAX/MIN functions on cells
formatted as percent.

You are possibly entering an improper formula, or not understanding the nature
of your data.

For help, please post your formula, your inputs, your expected outputs, and
your actual outputs.

--ron

percent is numbers>should work.