I'm trying to become a bit more proficient with this tool. I periodically get nonsensical answers from it, but those are diminishing as I figure out what I should be asking.

However, here's one I can't seem to figure out.

A train leaves Boston at 5am... wait, wrong forum!

Let's say I want to start with 5 gallons of must, to which I've added 20 lbs of honey. The calculator tells me that gives me a SG of 1.147 and a potential ABV around 20%. Easy enough.

Now, I want to stop the fermentation at 10% ABV. Alternately, I used a yeast with 10% ABV tolerance. What will the SG be when I get there?

If I try putting 1.147 into "current SG" and 10% into ABV, it tells me my target gravity is 1.08, but it also tells me to remove 9.199 lbs of honey from my must.

Logic tells me I can probably just divide the orignal numbers it provided (1.147, 20%) by the same number (in this case 2) and arrive at a gravity of 1.0725 and ABV of 10%.

So, how do I answer this seemingly simple question? Embrace the world of negative honey, trust common sense, or.... what?

Mahalo in advance!