From the article:
Pomegranate did refund PrimeGrid 3800 GRC (2100 GRC on 28 August 2017 and 1700 GRC on 30 August 2017). One would expect 1200 GRC more for a full refund, and 1200 GRC was indeed sent on 23 August 2017, but not back to PrimeGrid. Instead, those GRC were sent to an address where the GRC was consequently split up, some of which went to the wallet of user Tholo, an investor in Gridcoin. Source.
It was a 76% refund; PrimeGrid didn't get back 1200 GRC.
RE: Investigating the Pomegranate Network Mining Gridcoin