Getting a refund onto a paid-off credit card

Hi all,

I've been using a credit card to pay for small purchases, paying off the balance in full...just to build a credit history.

My question is:

I am due a refund for some tickets for a cancelled event, which will go back onto my credit card. My balance is currently so low that once I get this refund, I'll be in credit...how does this work?

I know it's probably an obvious answer, but I really don't know the answer as I'm new to credit cards.