Because I'm pretty sure my problems were with too much water, just how much of a boil are you supposed to have. A rolling boil? A simmering boil? Heck, taking the lid off vs leaving it on affects how much gets evaporated off. I have put numbers in to Brewer's Friend and 365 and am choosing the lesser volume one due to my first attempt. Practice... The nice thing is that even practice brews leave you with beer.
Since we are on the topic... With so many variables in play, how do you get any recipe to come out the same as the person who created it?
A gentle rolling boil used to be the norm, but there have been brewers that say a mere simmer (ripples on the surface) is enough. Some even claim leaving the lid on made no difference in retained DMS or boil off volume compared to leaving it off (Brulosopher.com).
You should know the boil off on your system, and use that number. If your calculator uses a percentage, then convert it to that. A gallon an hour is average. On my stovetop it was 3/4 gallon an hour, I barely had a simmer unless I left the lid on half way. That worked fine.
Then again, you'd be off only 1 or 2 quarts, not a big deal. Correct better next time.
Brewing a recipe the same as the guy who wrote it? Fat chance!
He couldn't even do it.
Some recipes are surely written better than others. You can get close as long as you know the grain percentages, OG, and AAUs (or IBUs) of each of the hop additions. Enter those into BF or Beersmith, then tweak to your equipment specs and efficiencies to get the same or similar numbers. But you still don't know how he fermented, the quality of his yeast, his water, and all those other factors that make each brew unique.
After all, why would you want his, your version maybe better.
It's very difficult on homebrew scale to even brew the same recipe exactly the same each time. Our variations are much larger because we're dealing with such small volumes (relatively).