In other words:

Low:      $0.5
Medium:    $1
High:      $2
Critical:   $10

The maximum of overall payouts will be $100

I don't understand why anyone should bother with such rewards. Even if you find the critical issue (I assume the one which would let you steal Ether from the contract) you get only $10, wouldn't it be better to just exploit the vulnerability and get 100...0x more?