A coin is in profit if the current price is higher than the price at the time it was last moved. Conversely, a coin is in loss if the current price is lower than the price at the time it was last moved.
Percent Supply in Profit highlights the percentage of the total supply which is currently in profit. This metric represents an oscillator that allows us to better understand the current state of the market for a given coin: in general, values above 95% suggest market tops, while values below 5% signal bottoms.
Percent Supply in Profit is calculated by dividing the absolute Supply in Profit by the total circulating supply and converting to a percentage.
Rafael Schultze-Kraft - Dissecting Bitcoin's Unrealised On-Chain Profit/Loss