What happens if I am late making a payment on my storage unit? How do late fees work?

Our late fee schedule only consists of 2 late fees per month. The 1st late fee is received when the bill is 5 days past due in the amount of $15.00; the 2nd late fee comes 15 days past the billing date in the amount of $30.00. In NEW JERSEY there is ONE late fee which comes on the account when your bill is 5 days past due; the late fee charge is 18% of the rent.