[modulo] Why does 2 mod 4 = 2?

I think you are getting confused over how the modulo equation is read.

When we write a division equation such as 2/4 we are dividing 2 by 4.

When a modulo equation is wrote such as 2 % 4 we are dividing 2 by 4 (think 2 over 4) and returning the remainder.