"Amount Invested" is different from the current value of a security or group of securities. It is a measure of the amount you paid for the security, but it does not decrease when you make a partial sale.
For me, it is useful mainly as the denominator in computing Return on Investment ROI
You are correct there's a difference. Amount Invested in the Portfolio shows the total amount ever invested in the security, with no subtractions for shares sold. The Security Report should show this Amount Invested at the top when the initial shares were bought or added. Unlike the portfolio view, the report subtracts amounts when shares are sold, so the bottom line will be different.
Now if you haven't sold any shares and the Amounts Invested are different, you'll have to give more information about what you're seeing.
As you have probably seen, there is a column for cost basis. Also if you group the Portfolio view by Account, you can click on the plus sign next to the security name to see the individual tax lots.
