If the accounts are posting at different times of the day, and the reports are all for the same 7 day period it doesn't make much sense that all the accounts would show exactly 250 posts. Given that they post at different times of the day.

I think this is an API limit on the analytics. From my cound of the Business Insider posts it looks like they're actually posting nearer 650 posts a week.

It's just being capped by the API to 250.