The 12V line is safe down to 11.4V and up to 12.6V. The spec calls for + - 5% or .6V for 12V, .25V for 5V and .165V for 3.3V so any voltages within those are fine.
To recap 12V is good for 11.4V to 12.6V, 5V is good for 4.75V to 5.25V and 3.3V is good for 3.135V to 3.465V. I hope that helps.
BTW, software readings can be very off so the best way to be certain of your voltages is to use a decent digital multi-meter to check the voltages.