In the Holdings tab of the Generator you will see the Market Value box. This is the sum of the current value of all holdings in that portfolio (at the latest close price).
Above that is the portfolio box showing the portfolio value.
These 2 numbers will be different if the portfolio has a cash balance.
The portfolio value is calculated by adding together the Market Value of the holdings and the current cash balance of the portfolio.
You can see the Current Balance of the portfolio in the Cash Performance box of the Generator Overview (last line):
If you don't want to have a cash balance in your portfolio, simply clear the opening balance by following these instructions.
Read this for more details of the difference between portfolios with and without a cash balance.