I DID get a couple of dollars too much reimbursement from Ipsos a couple of months ago. Sent the scheduler an email, and asked her to pass on the message. Never heard back-guess it was too small of an amount to mess with.
Happiness is not a goal; it is a by-product. Eleanor Roosevelt
The same thing happened to me a few months ago. I was told that it goes by the date they have been reviewed and sent to the client. So they may have all been shopped on the same day and reported on the same day, but if the editors didn't review them all by the cut off day then you wouldn't be paid for the other shops until the next payday.