Google wowed Wall Street with the revelation that its mobile business is generating revenue at a run rate of over $2.5 billion. Not bad for a business thats still in its infancy, and which was operating at a $1 billion run rate at this time last year. Of course, a run rate is not the same as revenue thatÂs been booked Â itÂs simply a way of extrapolating what a full yearÂs worth of revenue will be, assuming the current rate of revenue holds steady. So what is Googleâs actual mobile revenue right now? Many Wall Street analysts estimated on Friday that Google generated $625 million in mobile revenue in the recently-ended quarter -Â a not unreasonable assumption, given that four quartersÂ worth of $625 million totals $2.5 billion. (And since Google said the run rate was more than $2.5 billion, perhaps $626 million for the quarter would be an even more reasonable estimate). Not so fast, says BGC Partners analyst Colin Gillis. ThereÂs no guarantee that Google based its run rate on a full quarterÂs worth of revenue. They could have taken mobile revenue from the last month and multiplied it by 12, said Gillis. They could even have used their best single day of mobile revenue and multiplied by 365, he noted. As a result, Gillis estimates that GoogleÂs mobile revenue in Q3 was probably closer to $500 million or $550 million. âWe have no idea what that number really is,Â he said.