As I have said, it is not considering the service quantity (which is showing in Service tab). It is calculating PR quantity with compare to PO quantity.
You PR quantity is 1 AU and also your PO quantity is 1 AU.
So when running ME5A (without tick of Closed Requisition), system will consider only these PRs which has the higher quantity than correspond PO.
Here your PR quantity equal to same as PO quantity, so ME5A is considering this PR as completed (closed).