Hi,
1. Create independant good receipt for 101 Qty, credit account sholud be the one used when good issue.
2. Create the Ap credit memo for 1000 pcs. (if the base document closed do it standalone)
3. Create the new GRPO with correct one for 1000pcs.
4. issue the 101 qty as same you did before.
Regards
Sridharan