This is our proprietary skill rating calculation. This has nothing to do with official game ranking or MMR.
The purpose is to show player skill levels relative to other players, not estimate MMR.
PASSIVE - Every 8s the highest health enemy minion or jungle monster within 80 units of you is marked. If you secure the killing blow on that target you gain 4 bonus gold and 25% attack speed for 8s, and restore 30 Mana. Can be upgraded at level 20.