For the statement 2+2=4 to be true there are some assumptions that needs to be. That is 2+2=4 is true within a system, mathematics, but this system is in fact a construction!
The basic assumption here is that we can define and identify 'one' thing - say a ball, a man or any other "item" - for this to be true you would further need to have 'identical' items... that is items that have very similar attributes.
As you can see this leads to a infinite regress, where one assumption leads to others, and in fact we don't have such systems in reality, that is such systems are only 'real' in our minds.
Thus we can construct system where one object can be exchanged 1:1 directly, say money in a computer system,, but there are few if any such systems in the real world. In our constructions we can agree that one ant is equal to an other, but in the real world they may be very different.
So the idea of the piles of sand are very much to the point. There is never such a thing as one man or one cow - and 2 + 2 cows is 4 cows only if we agree to what one cow can be.