Where did you find this? I can't find it on the main page which is where it was last year.
ETA - Nevermind I finally found it in Discover Special Offers and Earn.
I also noticed in that section there are some Mercury Magazine free magazine sign ups for 50 sb, which goes pending 32 days. But this is a legit place, I've gotten a ton of mags from them but you have to be new to them and I don't know if it goes by email or mailing address. So far I've seen Cosmo and Town and Country. I haven't paid for a subscription in years and use them and a couple others. And if you already get the mag but are new to Mercury still do it because it will just add on to your subscription as long as the info matches. I think my Better Homes and Garden doesn't run out til 2022 and Martha Stewart 2020. I'm on hunt for US Weekly because it'll run out next year