"Buy and Hold" over time in Performance

Jay Gourley

The explanation of buy and hold says:

• To calculate the hypothetical value of investments in a Buy and Hold scenario, Quicken retrieves from an external data source the total returns (taking into account dividends, stock splits etc.) of each quoted security (stocks, mutual funds) present in the Selected Accounts at the starting date. For subsequent dates, the hypothetical value is computed by multiplying total return ratios for that date for each quoted security by their pro-rated proportion of the starting cash and securities portfolio. The external total return calculations assumes that dividends and distributions are reinvested.

What does that mean? In particular what does total return "at" a start date for a security? Does it mean total return "since" the start date? And does the cash yield setting just apply to uninvested cash in the chosen accounts?