How much do I have to pay for my cellular data?

It's my first phone, an iPhone and I don't understand the gigabytes and the megabytes thing. Its also a contract phone. I don't want my dad to take it away from me if the bill cost too much. This is what it says sent 36.6 MB. Received 298 MB. Please Help me thanks.

Added (1). Mine is unlimited! Oops forgot to put that but thanks.

It all depends on your 'Allowance' and how much data you are allowed to consume. My personal contract has unlimited internet data so I don't have to worry about anything. But what I advise is that you ask your dad to ask the network what the data allowance is, and you should stick that. When it says 36.6mb sent, this means how much mb or data was uploaded to the internet, and the received means how much data was downloaded.