No, it is not normal. And rebooting is also not necessary. What you probably did not do is hit the Enter or Tab key after entering the max power value. If you just enter the value in without hitting either of those keys, the value does not get set. All fields where manual entry is required in the Setup window, require hitting the Enter or Tab key after the text or number is entered.
I just retested entering a value for max power and I set it to 5 different values and it was set properly each time.