The Product: They're advertising a Super Special of 10 GB "broadband" internet per month. If it was from any provider other than Xtra or Vodaphone, it might even have been a reasonable deal. (Xtra is infamous for so-called "broadband" that's barely faster than my dial-up used to be before IHUG slowed down back when IINet owned it; and Vodaphone are so incompetent that they thought that buying IHUG of IINet would get them into the internet market without having to do any more work.)
The Advertisement: Some indeterminately aged youngster (maybe about 14 years old) is standing chest deep in a room filled with jellybeans. These jellybeans symbolise 10 GB of internet. Each one is an email, and, (here a small amount of jellybeans - maybe a small bucketful - is tipped over the boy), "that's a movie".
The Calculations: Assuming a reasonably sized room (the room in question looks a bit like a lounge), a measurement of 3m x 3.3m (10 ft x 11 ft) would be reasonable. That would make 10 m² of floor space, and, assuming for the sake of easy calculation that chest high on the youngster is 1m (3 ft 4 in), that would make 10 m³ of jellybeans symbolising 10 GB of internet. While the amount of jellybeans tipped over the youngster is difficult to tell, it looks like a small bucketful; I'll be generous and assume 0.1 m³ (about 3 ft³).
The Dishonesty: This advertisement implies that a movie downloaded off the Internet would be about 100 MB. I did a bit of asking around on IRC the other night, and people who have actually managed to download movies off the Internet have advised me of various sizes of various movies; the smallest was about 600 MB and the largest was over 1.3 GB. Assuming for the sake of this exercise that a typical movie would be 1 GB in size, this means that the Xtra advertisment is false and misleading in implying that with 10 GB of internet, one could download 100 movies; whereas in truth one could only download 10 movies.