Payables Auto & Manual Release Criterias

What criteria determines if an invoice hold is release manually or systematically?  In these scenarios there are 2 different invoice with the same holds, but one was released automatically and the other had to be released manually.  They both had the same holds, but different release types.

Holds:

Max Qty RecQuantity billed exceeds quantity received by tolerance amountMatching Hold ReasonQty RecQuantity billed exceeds quantity receivedMatching Hold Reason

Release:

Invoice Quick ReleasedHolds released in Invoice Holds windowInv Quick Release Reason * Manual ReleaseMatchedPassed matching conditionMatching Release Reason * System Release

Thank you