just to keep up with the interes Does the following sentence mean "4500 francs was only the interest of the money per month" or "4500 francs was the interest plus the main monthly payment (meaning the total amount that should be paid monthly)"? Context: Though 15% interest seems normal to anyone with a credit card, in the 19th century, it would've been considered fairly high. In real terms, it meant that Maelzel had to clear 4500 francs per month -- no small amount -- just to keep up with the interest.