Its difficult to diagnose completley but my guess would be either there is an issue with the unit or you didn't let the battery charge fully after unpacking and testing. The battery is not always at 100% out of the box. With that said, I would not test again on that UPS, your first test probably knocked a few hours of life off that bulb.
In fact, I would reccomend if you can return, it do so. The 5010 is not an inexpensive device, upgrade to a higher end Cyber Power which offers built in LCD and wattage readout. I own the Epson 8500UB, I paid $1,800 for it back in 2010. It has its own, 1000VA UPS which was less than $200. Good investment.