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 - On Basic Attack hits, deal Physical Damage equal to 1.5% of the target's maximum Health. If the target has over 2000 Health, the bonus damage scales up. This effect reaches a maximum of 6% of the targets Maximum Health at 2750 Health.