Hello,
As per the standard SAP system design system allow to confirm to GR more than the confirmed quantity.
You can use the Auto Good receipt functionality through production scheduling profile CORY to have confirmation quantity = GR quantity
If you don't want to use Auto Good receipt functionality then you need to go for an enhancement.
like BADI - WORKORDER_GOODSMVT using the method - MANUAL_GOODS_RECEIPT or User exist MBCF0002.
Also refer this document,
Without GI confirmation and without confirmation GR is not possible
Best Regards,
R.Brahmankar