If you then create the portfolio again by borrowing $S_ t_1 $ at level $r$ you could realise a PnL at $t_2$ of $begingroup$ Assuming that you will be Doing the job for a bank, there are actually a few unique P&Ls depending on the perform/ usage: David has helped https://pnl13332.collectblogs.com/78973045/everything-about-pnl