Basic 5% range is
+12V....11.4V to 12.6V
+5V......4.75V to 5.25V
+3.3V...3.135V to 3.465V
however software monitoring is really only good for observing realative changes, not definative values, for a true value youd need to check it with a multimeter
which is why you have the option in MBM to calibrate