Do I need to sell stock to effectively use the German Sparer-Pauschbetrag (and if so, how much)? (opens in new tab)

In Germany, 801 Euros are exempt from the capital gains tax ("Sparer-Pauschbetrag"). There is a small tax on unrealized gains ("Vorabpauschale") but it is afaik negligible right now, and few of my investments pay dividends. What isn't clear to me is if the Sparer-Pauschbetrag will be applied retroactively. Say I invest 10K and after 10 years I sell for 15K. Would I be taxed on 5000-801=4199 Euros, or on 5000-(10*801)=0 Euros? And if it's the former (which I assume), does that mean to take ful...