fomo tracks your profit and loss on every position, whether you are still holding or have already sold.
While you are holding a token, the percentage shown on the token page and your profile reflects your total return on that position. This includes the current value of what you still hold and anything you have already sold. It updates constantly as the price moves.
When you sell, your realized PnL is calculated based on what you actually received. If the price moved between the last displayed quote and the on chain execution, the realized return reflects the execution price, not the quoted price. On tokens with lower liquidity or higher volatility, the difference can be larger.
The chart on your profile page is separate. That reflects your total portfolio value (cash balance plus all holdings at current market price), not the PnL of any single trade. When funds leave your wallet through a withdrawal or transfer the chart adjusts because the value is no longer in your account.