Is rest of the machine at that level?
Components and monitor are important to know because those affect to how much power is needed just for chance of succesfull transfer to battery mode without UPS "falling on its knees" instantly.
Another thing is that PSUs aren't at their best comfort level when fed modified square wave so there needs to be decent margin between PC's power draw and UPS' output capability.
And that number in model name of UPS is just apparent power/VoltAmperes which isn't same thing as watts when talking about AC.
If actual watt rating isn't advertised it's usually something like 60% of VA rating, with better ones reaching 70% and worst down to 50%.
As for need to clear CMOS before succesfull booting new BIOS/RTC battery would be worth of try.