mine is 180-200. I use it with each thread change. It's been a life saver for me as I just could not get the hang of using the drop test.
Since I only quilt for myself, I'm not using a lot of different threads or battings, but so far I don't look up anything or write down anything. I started out with it a bit higher, but found closer to 180 is the "sweet spot" for my machine.
I also have a digital readout for the top tension and have set it anywhere from 500-800 to get a good balance. Those numbers are also meaningless in themselves.
The two gauges measure differently, one you set the tension (screw) to get a constant pull of 180, the other you are getting a readout of the pressure that is applied to get a specific pull. In both cases you are changing the pressure to get a specific pull.
It's very likely the top pull is also within a close range, but there is no easy way to measure it so you are stuck with knowing what to set the pressure at to get that for each specific thread. So a lot more to remember.