No idea, it's definitely good that it lead you to Steemit.com.
I challenge you to see if you can earn more than from the Genesis mining contract (0.1 STEEM) from posting on the platform 😉
If you're interested, I'm giving away a prize pool of 75 SBD; that should blow away the ROI that you get from Genesis mining ☺️
Researched more - I don't think GM is actually mining STEEM after all. I think it's still mining ETH and converting that to STEEM somehow.
I guess through an exchange - they can work out the rate of ETH / BTC and BTC / STEEM to work out the exchange rate of ETH / STEEM.
That's actually how some foreign exchange rates are worked out - usually via USD.