businessofapps.com claims they only do 8M transactions per month, and have/had 4500 employees, so 8M transactions / 4.5K employees / 20 working days/month that's 88 transactions to post per day.

They don't need datacenters, quill pens and paper accounting could handle that 200 years ago with about 3 hours work per day.

Generally supermarket cashiers can do somewhat less than 30 transactions per hour, so I think its justified they should be able to do all the accounting manually in three hours.

The numbers do look a bit odd.

Yeah, the right number is probably somewhere between 10 and 4500.