@Jack, and I don’t quite get what’s not clear for you there 
But the main point is if @Kuto understands what was meant?
Since he’s already put some thoughts into the “tedious but transparent calculation” method (vs. hidden map() with int maths), I rather tried to offer support from there, than “confuse” him more than necessary.
So, @Kuto have we confused you even more now, or are you good with us 
Off topic:
map() is actually nothing else than “calculation method”.
In the given case, it just goes together with a different set of “anchor points” (0…3.3 plus voltage devider constant vs. measured min/max ADC value/voltage).
map() just hides the maths from the user and due to the hidden integer nature the given results might not always line up with what you’d expect when checking with a DMM and doing the maths on paper.