Here is the law: 718.116(c)

"Assessments and installments on them which are not paid when due bear interest at the rate provided in the declaration, from the due date until paid. This rate may not exceed the rate allowed by law, and, if no rate is provided in the declaration, interest shall accrue at the rate of 18 percent per year. Also, if the declaration or bylaws so provide, the association may charge an administrative late fee in addition to such interest, in an amount not to exceed the greater of $25 or 5 percent of each installment of the assessment for each delinquent installment that the payment is late. Any payment received by an association shall be applied first to any interest accrued by the association, then to any administrative late fee, then to any costs and reasonable attorney's fees incurred in collection, and then to the delinquent assessment. The foregoing shall be applicable notwithstanding any restrictive endorsement, designation, or instruction placed on or accompanying a payment. A late fee shall not be subject to the provisions in chapter 687 or s. 718.303(3). "

I am still searching for authority on the compunding interest and will be back with you shortly.