Difference between Qty Invoiced & Qty Billed - AP Invoices

Hi,
We entered a PO with the following lines:

PO Line 1 - Quantity=5, Price=100
PO Line 2 - Quantity=5, Price=250
PO Line 3 - Quantity=5, Price=300

We then received the PO as per the following quantities:

PO Line 1 - Quantity=5
PO Line 2 - Quantity=5
PO Line 3 - Quantity=4

We entered the AP invoice matched to the PO

PO Line 1 - Quantity=5, Price=200
PO Line 2 - Quantity=5, Price=300
PO Line 3 - Quantity=5, Price=250

For Line 3 the Invoice was Placed On Qty Rec Hold.

The issue that we have is that in the Invoice Lines the Quantity Invoiced for Line 3 is Quantity = 5 but when we check in the 'Hold' tab the Quantity Billed for Line 3 is 4.833333333333333. We don't understand why, because we expect that Quantity Invoiced will be equal to Quantity Billed. We expect 5 because when we matched the invoice to the PO we matched by 5.