This error occurred on August 18. Attached is a copy of the report - the numbers just don't add up. When I signed it that day, the balance shown to me was -$1.49 (which surprised me, I thought that was impossible!), and I had to add funds. Yet their report (below) shows I should have seen a starting balance of $5.62.
On 8/17 they processed a credit of $3.45, but I don't think that has anything to do with it as the missing total is $7.11.
I would have reported it immediately but I have had to try 4 different browsers to successfully create an account and add a password with ZenDesk. I also reached out on Twitter but with no answer.
If this is an issue to take up with Stamps.com please let me know how to do that. They, of course, don't have me as a customer.