An average like that takes into account many people hardly using their phone so there is nothing much to report, or using it in a bursty manner so there is nothing to report most of the week but plenty at the weekend.
The "150m devices" claim is rather vague too. It will no doubt include devices that are no longer in use, like when a dating site claims to have X million members without mentioning the fact that all but a few thousand of them haven't logged in for many months - they can truthfully claim such devices have the software installed but that will skew the average bytes/device/day taken from the released figures downwards.
A rule of marketing (which includes selling the company to prospective employees if they are looking for them on linkedin): Never lie when you can selectively use honest statistics instead.
333 bytes is enough to send plenty of information, like your favorite apps and how long you used them. Consider something like: "com.android.browser:1.4h;1-800-HI-THERE:2.3min", which is only 47 bytes.
The "150m devices" claim is rather vague too. It will no doubt include devices that are no longer in use, like when a dating site claims to have X million members without mentioning the fact that all but a few thousand of them haven't logged in for many months - they can truthfully claim such devices have the software installed but that will skew the average bytes/device/day taken from the released figures downwards.
A rule of marketing (which includes selling the company to prospective employees if they are looking for them on linkedin): Never lie when you can selectively use honest statistics instead.