Simplify the following text for a Grade 11 native English-speaking person.
Original: In mathematics , modular arithmetic ( sometimes called clock arithmetic ) is a system of arithmetic for integers , where numbers `` wrap around '' after they reach a certain value -- the modulus .
Simplified: Modular arithmetic ( sometimes also called Modulo arithmetic ) is a way of arithmetic calculation with integers . Numbers wrap around once they reach a certain value ( called modulus ) .