Whenever I go into the review section, there is never just 1 question there. It comes up in batches of 7 or 10 at a time, mainly in First Posts. Why is this? Does it actually send out batches?
A scheduled task runs every five minutes and populates the queues with qualifying items that haven't previously been added.
Given the amount of traffic on Stack Overflow, it's quite likely that more than one thing happens in any given 5-minute interval.