There are two different floating glass meters for meters for distilling. One tells you the potential ethanol content if your mash. The other tells the the final proof or percentage of ethanol. The content of your starting liquid determines the safety of your operation. It’s a lot safer to turn 80 proof into 190 than it is to turn 151 into it. The starting liquid needs to be heated so you can do the math in wanting to keep that below boom boom level.
it’s a percentage game. 80 proof is 40% so if you were able to get 190 on first pass it would be no problem to get 45% off the starting volume of 80 to now be 190. It can be done with just one pass quite easily. Just had to be slow. Secret is keeping it right in the drip drip drip zone. Slow and low. I can run a Sugar shine run pretty close to190 first pass but I have a tall column and know how to slow it down which helps a lot. I run bourbons 140-160 proof and rims down around 120-140. Lower the proof of the still the more taste in the end product. Then it gets tempered.
I threw up a few pictures of a little vacuum still in my Megabuds, rosin and tinctures thread, you can run it with or without vacuum to do mini still runs and make any alcohol you want. Or you can distill vodka into everclear. If using a small still with a 20% mash just be aware your end product will be 20% of starting volume. Which might not be much.