credit for payroll is a common practice. Do you think your company has cash reserves on hand every day for the amount of your payroll check? No. In the most simple terms. They use a line of credit to cover any amount not in an account when payroll is drawn. The line of credit, in most cases, is tied to the company's accounts receivable and is paid back when funds are in to cover the difference.
You shouldn't see CREDIT and think Amex card at 19%, think short term, 2-3 days loans @ 4-5%.