Traders chart these aggregates like an index. TOTAL tracks the whole asset class, TOTAL2 removes bitcoin to show whether the rest is participating, and TOTAL3 also removes stablecoins so the series is not distorted by cash parked in tokens.
The figures are soft. Market cap multiplies circulating supply by last price, so thin tokens with small floats and enormous fully-diluted-valuation inflate the total, supply figures vary between data providers, and assets with almost no liquidity carry the same weight per dollar as deep ones.
Used carefully it is a sentiment gauge rather than a measure of capital. Actual money in the system is closer to stablecoin supply and realized-cap, both of which behave very differently from headline market cap during a drawdown.
Related: bitcoin-dominance, altseason, fully-diluted-valuation, realized-cap