A quarterly report reflects earnings. There is no "quarterly population report". You can talk about the money you have made to a certain point, but the population numbers of a game can come from anytime. They can be peak times, they can be from early or late or even after the report time they are covering because they have an impact on the earnings in the future.
I believe some people think that an earnings report will include a printout of the game's population from March 31st. This is not the case.
(Also, as a complete side note, a "quarterly report" does not always mean Jan 1 - Mar 31 and etc. through out the year. Many companies operate on different quarters. Some start in October, some from the middle of the month, etc. The only laws that govern a "quarterly report" is that you can't lie in it. That doesn't mean that anything in a "quarterly report" isn't up for interpretation.)