I think its comparing how the algorithm did versus just blindly HODLing your coins. So HODLmeter:XX% is the percentage the algorithm increased the value of its

I think its comparing how the algorithm did versus just blindly HODLing your coins. So HODLmeter:XX% is the percentage the algorithm increased the value of its holdings over the described period. The HODLing is the percentage the market increase by over the same period. Thus, if you had HODLed for the same period for ETH, you'd have lost a significant amount in the value of your holdings, but the algorithm made money.