So finally I figure out why does it happen

Here is the explanation hope u will understand it

So first of all we know that if we add two same numbers and divide it by two it will give the same number right
For example: (a + a)/2 = a (a is a number here)

So here you can notice I am taking difference between the given two number (or you can say absolute difference so it will be positive) so if we add the difference in the smaller number it will make the smaller number equals to the bigger number thus the both number will be same and results in the same number (remember that (a+a)/2 example?) which will be the bigger one