I'm no lawyer and have no special knowledge, but this is for "new account" and represents log files, according to the suit. I can almost guarantee Google will show the data is some kind of anti-fraud/spam analysis (thus why it doesn't wait for you to get on wifi).
This it's not an apples to apples comparison (they are only guessing the logs are for ads, but the suit doesn't appear to actually show evidence that the data is advertising related). Similarly, they extrapolate that it will continue to log that much data forever, but it may be related to the fact they are new accounts, and data usage may drop off after the account gets some history behind it.
But hey, I'll be happy to take a class action payment, I just don't see this actually going anywhere.