The linked press release from Riot is infomative. They've more than doubled their hashrate from 4.8 EH/s in August 2022 to 10.7 EH/s in August 2023 (they technically have 10.7 EH/s^2 but I think that's a typo stemming from the confusion of whoever made the chart).

The hashrate also went from ~202m TH/s on August 1st 2022 to ~373m TH/s on August 1st 2023 (source: https://www.blockchain.com/explorer/charts/hash-rate). That means Riot was able to increase their share of the overall hashrate, and that doesn't even include their ~17k offline miners stored in the building that was damaged in December 2022 (also mentioned in the linked Riot press release).

The offline miners would lead to a 17% increase on top of Riot's deployed miners if they were able to get offline, so it makes sense that Riot is selling energy back to ERCOT during this period of poor utilization of their resources. It still makes sense to sell energy even with full utilization of miners sometimes, but I thought it would be interesting to add this bit of added context.