Use authoritative guidance to identify the logical flaw in the following scenario and explain in plain english what this means.

2) Blue Devil Corp. charges an established customer $5,000 for a delivered good and offers a 10% discount if the balance is paid within 10 days. The customer has never missed a payment deadline, but has never paid quickly enough to take advantage of an early payment discount either. Conservatively, Blue Devil Corp.'s accountant credits sales revenue $4,500 at the time of sale