Does no additional cost at $0.00 on your plane ticket date change mean you pay the same price as before?

My Aunt bought a plane ticket for me and i dont know what price she paid for it but she gave me the conformation # and i need to change the date because i need to be back before the date that she set but i dont want to pay any extra money so i went to change it and it gives me the new price but i dont know if its more but it give me the pending air itinerary and then it says additional amount due $0.00 so does that mean i dont have to pay any extra?