Concept Of "Price Variance Accounting" Entry On Matching Invoice to PO in AP

We can understand the Price variance concept by the following examples,
Create and approve PO qty=100 price=$5 for total of $500
Invoice is matched to PO qty =100 price = $1 total of  $100



Here The invoice has a lower price than the price on the purchase order
In Oracle Payables, enter an invoice.
(Invoices->Entry->Invoices-> Match an expense invoice to a purchase order, by clicking on  match button,Accounting entries for the transaction with price variance:
debit to the expense account    $500

credit to the expense account      $400
credit to the AP liability account  $100


Here the price variance account for the invoice is determined
after matching to PO according to the following rules:
1) If the Destination Type is other than EXPENSE, the price variance account 
will be PO distribution variance account
2) If Destination Type is EXPENSE and accrue on receipt is Y, the price 
variance account will be the PO distribution Expense Account
3) If Destination Type is EXPENSE and accrue on receipt is N, the price 
variance account will be the invoice distribution expense account