How do you check data usage on the N900?

Sorry for starting a thread on this. I know the answer is very simple because I have bumped into it like 5 times in the past. But as is typical now that I need to actually use it I just can't find it despite searching for it over and over.

Going abroad next week and mobile phone company does 10mb data usage whilst roaming for £20. So need to check to make sure I don't go over 10mb. Also want to check my usage between now and my trip to see if 10mb is enough. Come to think of it that is ridiculously little isn't it?