It is probably a moot point so long as you are running ok.
A psu will only use the wattage it needs, regardless of the max capability.
It is not wrong to overprovision a bit.
Most of the pc power demand comes from the graphics cards.
This chart does an reasonable job of figuring out what you need.http://www.realhardtechx.com/index_archivos/Page362.htm
If you want, disconnect the ups power from the wall and see how long it can keep your pc running at the load you want.