Sort:  

The Steem Supply data shows rewards pending over the forthcoming 6 days (< 7 days pay-out).
The metric "total rewards fund" (currently worth: $ 668847 USD) is the total reward pool on Steemit over the forthcoming 6 days (< 7 days pay-out).

Ah I thought it was related to my account in specific, that's why it seemed so weird and way too big. Thanks :)

It is actually! Below that figure it also displays what percentage of the total rewards fund will go to you! Is it bigger than 15% already? ;-)

No, 0,3% potential growth and 0,0000% of pool

Aiiiii, you need to step-up your game then! For me it's currently Potential growth: 72,90%, (account is getting 0,0006% of the reward pool)

;-)