Supervised loans, in which the rate of loan finance charge exceeds twelve percent per annum, not made pursuant to a revolving loan account, in which the principal is one thousand dollars or less, shall be scheduled to be payable in substantially equal installments at equal periodic intervals except to the extent that the schedule of payments is adjusted to the seasonal or irregular income of the debtor, and

(a) over a period of not more than thirty-seven months if the principal is more than three hundred dollars; or

(b) over a period of not more than twenty-five months if the principal is three hundred dollars or less.