DPI measures actual cash returned. A DPI of 1.0× means the fund has returned all the capital LPs put in; anything above 1.0× is realized profit. DPI is the metric LPs care most about late in a fund's life because paper marks (RVPI) eventually need to convert into cash.
For venture funds, DPI tends to lag TVPI by years because exits (IPO, M&A, secondary) happen on long horizons. A fund with high TVPI and low DPI for years past its expected liquidation cycle is a yellow flag.