Interest?

In the grocery store the check-out person always asks "Cuantas cuotas?" which at first Mike took for "Cuantas copias?". The later meaning, "How many copies?". I thought that was odd but Mike figured it was because we are diplomats and get the tax back so we may want more than one copy. Sounded good to me. After a few weeks of listening I realized it definitely wasn't "copias" but I wasn't sure what it was. Then I figured it was "cuotas" and translated it to something like "How many quotes?" kinda like a written estimate only it's not an estimate. Don't laugh these things happen in foreign languages. "Cancelar" means you paid your bill not cancelled service and you give a test here not take a test so it's possible! Anyway, turns out it means, in general don't aske for direct translation, "how many installments". Basically when I go to the grocery I can pay part now and part 2 weeks from now, or next month, next year... Not really sure of the details but you can split your bill up. I'm thinking this is only for credit cards but can't say for sure. I wonder if there is interest?