Refund deposit

I moved out of an apartment in centurion on 29 April 2017 and made a payment of R1500 on the 15th April 2017 when my actual bill was R927. Fourteen days later I moved out and put a notice that I was vacating the premises in 48 hours as stipulated on their forms. After calls and email of over 2 months requesting my deposit, they refunded me R533. How on earth can fourteen days accumulate to R1,240?I am sick and tired of vultures like Impact meter services. They are frausters!