Currently, if you add cash to a portfolio, VectorVest calculates the addition as if your portfolio gained that much through trading, and if you withdraw money from a portfolio, VectorVest calculates that as a loss. Depositing and withdrawing money to or from a trading account are activities that investors do on a regular basis. Such transactions should not affect the G/L%.
The workaround for this calculating error is to modify the opening deposit. Modifying the opening deposit does reduce the effect of this miscalculation, but it also slightly reduces the G/L percentages since the gains and losses will be calculated against a larger or smaller balance than what was actually in the account at the time.
Correcting this is a must for anyone who uses portfolios to track an actual portfolio.