Posting Quantity and Price Variances 
The account movements made when quantity and price variances occur depend on the type of
price control defined in the material master record, in the same way as for regular price variances.For the posting selected with an asterisk (*), the following must be considered:
Postings in the Case of a Material with a Moving Average Price

Goods Receipt
The material is debited with the purchase order price at goods receipt,
that is, with $600 instead of $660.Invoice Receipt
When you enter the invoice, this $60 has to be subsequently debited.
Goods Receipt at a Later Time
The GR/IR clearing account is cleared when the expected goods receipt of 40 pieces for $440 arrives. The offsetting entry is then posted to the stock account.
See also:
Material with Standard Price Material with MAP with Stock Coverage