The potential part is based of the 10 minute production time scale, if you switch to that time scale those numbers (1.8k and 1.1k) should match up and be the same. Unfortunately the selected time scale is not available to mods so I can not make it change based on which time scale you have selected.
The short freeze when opening the production window is because it has to scan the entire world for every crafting machine to calculate your potential. Even on my giant save with 30,000 crafting machines it was not slow enough to go with a different and much more complicated method of doing it.
If the data displayed is good or bad is up to you. If the bar is 50% full you could be producing twice as much with your current machines if you feed them more input/used more of their output. You'll have to check outside factors like if the output is backed up, input lacking, or anything else. I personally use it to see where the problem is. If I see I'm lacking red circuits for example and I check the potential and see they're working close to 100% then I know I need more red circuit producing machines. But if I instead see they're only working at 50% then I know there are input materials missing and check on green circuits and plastics and so on.
