It would be a good idea to track the full history of gains and losses on the instrument screen.
Whenever I reduce my position in a stock, the investment performance is calculated as a percentage on the residual amount.
Any losses from the partial sale disappear from the instrument screen and need to be worked out manually.
If I buy 10x shares @ £20 = £200 value
Then the share price falls to £15 = £150 value
This equates to 25% paper loss, displayed on the app as a £50 loss
If I sell 5x shares at the £15 price = £25 actual loss
Then I have 5x shares remaining at £15 = £75 value
The app will show a 25% paper loss on these shares, so £25 down, but I have also crystallised a real loss of £25 by reducing my position which I can’t see on the same screen.
I am basically down by £25 + £25 on the stock historically, but the app won’t tell me that.