After you know the wattage of your load, use the Runtime tab on the product page to see how much runtime you get at a given wattage.
https://www.cyberpowersystems.com/product/ups/smart-app-lcd/or1500lcdrm1u/
The one you have selected will have 2 minutes of runtime ~900w on a fresh battery. If all you want to do is clean shutdown, that’s probably fine (as long as you don’t have brief power drops that you want your shutdown procedure to ignore). If you need more time then you’ll need a different UPS.
Note that some UPS models will do better for a given task than others with similar specs. For example I have a ~100w homelab, and wanted maximum runtime for 50w during a power outage (servers off, router+switch+aps active). Some similar spec Cyberpower models were ~120 minute runtime at 50w while others were 200+ for the same load.
Correct. And as AtariDump points out, it’s best to check typical runtime wattage, not peak, and not just on specs.