It calculates based on volume of the combined ingredients. I assume dissolving 1 pint of honey in 9 pints of water will result in less than 10 pints of total volume. I don't know exactly how much, but guessing 9.5 pints total, and using raw honey and raisins as the fermentables, I get 11% ABV with the high attenuation D47 yeast, and 8.7% with the low attenuation S-04.
Caramelization will reduce the fermentability of the honey, but I am not sure by how much. My guess is that it's a small effect.
(All this is wrong, go to edit) I would expect this mead to be high ABV, in the 12-13% range.
The rule of thumb I've heard, and has been good in my experience is 1.035 SG per 1 lb honey per 1 gallon of water. The 3 lbs in 1 gallons would come out to a ~1.105 SG, which is a bit over 13%.
Though, the sugar content of honey varies from batch to batch, and the non ferment-able sugars from the caramelization process, I would expect anywhere from 9-12%. The more caramelization, the more "burnt sugars", the less ABV.~
EDIT: I grossly miscalculated the weight oz to lbs. This is only 1.5 lbs, which would be ~5-6%, making it more akin the ABV of a beer. Same caveat that it would have probably been lower due to the unfermentable sugars.
https://www.brewersfriend.com/homebrew/recipe/calculator
It calculates based on volume of the combined ingredients. I assume dissolving 1 pint of honey in 9 pints of water will result in less than 10 pints of total volume. I don't know exactly how much, but guessing 9.5 pints total, and using raw honey and raisins as the fermentables, I get 11% ABV with the high attenuation D47 yeast, and 8.7% with the low attenuation S-04.
Caramelization will reduce the fermentability of the honey, but I am not sure by how much. My guess is that it's a small effect.