For water, your quantity is not “1”, but rather “blob”. So, yes, blob+blob=blob, but none of those are integers. When they combine, it’s not the math that changes, but rather the means by which you measure it. In different units, such as one gallon plus one gallon, the math holds true.
Blob is not a quantity, its a thing… You are acting like the question “How many blobs do I have” cant be “1”.
The problem is “quantity” depends on “the quantity of what exactly”.
blobs are measured in integers and yes 1 is a valid quantity of blobs. Blobs (like ducks) can also be measures in volume, in which case 1 m^3 + 1 m^3 = 2 m^3. But i wasnt measuring by volume, just as i didnt measurte by volume of ducks, i was measuring by unit, as we do with ducks.
If i make a duck into ground meat, and make it into sausage I can say “I have 1m^3 of duck meat” or I can say ““I have a pile of meat here that is 2 ducks of meat”. Both are just as valid as the other.