PO encumbrance vs uninvoiced amount

Hi,

I have a scenario where the encumbrance amount on the PO doesn't match with the Un-invoiced amount in the PO activity page( under Invoice Tab). This PO has 1 line and 6 distribution lines( different Project-Activity). This is from a requisition with 1 line and 6 distributions. There are three vouchers created for PO line 1.While the PO is distributed by quantity, the vouchers are all distributed by Amount. The Un-invoiced amount= Total PO amount- Total Vouchered amount. On the Review PO Information page, if I go to the distributions for the line 1, I can see the encumbrance balance(