UPS backup question on iMac with Snow Leopard

I am using a UPS backup battery with a USB connection with my iMac with OS X Snow Leopard. I have the Energy Saver System Preferences set such that the computer will shut down when the UPS battery level is below 50%. What happens if the iMac is in sleep mode when the power goes off? Will the computer still shut down when the battery level is below 50%, or will it stay on?

thanks, Kevin