USALS is only for finding a satellite, in my opinion. Once you find the satellite, I switch over to diseqc mode, manually use Fine Movement to rock the dish west and east to find the highest reading and save the position to a unique memory location.
My experience is that using Calibrate tells the dish to move east and west, measuring received signal of the current satellite. It does this many times to automatically find the highest reading. It concludes by reporting the difference in azimuth from the original setting. I don't use it much. Auto Focus is a mystery to me. It seems to be like Calibrate but endlessly rocks the dish back and forth without really accomplishing anything.
Calculate will do a global change for all satellite memories. I've never used it.
When it's time for a tweaking of the dish, I switch to USALS for LPB on 87W and NBC on 103W. I use the Edision app on my smartphone that remotely shows received signal on any satellite and only take the smartphone to the dish. I then manually move the whole assembly slightly to peak these two tps. When they are peaked, everything else will be good. I then switch back to diseqc mode, and manually repeak and save each satellite, if necessary.