Static frequency tolerance sets the acceptable input frequency range, when its outside of that the UPS takes action. If the target frequency is 60hz and you set 5% tolerance, then the UPS will override if the incoming frequency is outside of 57-63Hz. Most utility supply regions have a tolerance of somewhere around +-0.5Hz. Low quality generators may have much larger range. Many (but not all) computer type equipment can function with 5% frequency tolerance. Some types of motorized equipment require tighter than 5%.
Slew rate sets how fast the input frequency is allowed to change before the UPS takes action. A setting of 1 Hz/s means the input frequency can change from 60Hz->61Hz no faster than 1 second before the UPS overrides. I don't know what the large utilities supply, but it's probably going to be low. A low quality generator might have much higher values (especially if equipment will be dynamically loading generator). If the output load is something that can not change quickly (for example a large motor with large inertia), then you'd likely set the slew rate on the lower side. Many computer type equipment power supplies (switching) are more tolerant, so you could set higher in many cases.
In both cases, you'd likely set these between whatever tolerance your source provides and whatever tolerance the equipment can take.