The grouping feature allows multiple purchases and sales to be merged. So it may be that the profit differs when the buttons are activated or not (and either the closing balance or the profit of the following years compensates for this difference).
For example:
Buy 1 BTC for 1000 EUR on 01/01/2020
Buy 1 BTC for 1500 EUR on 01/01/2020
Sell 1 BTC for 2000 EUR later in 2020
Sell 1 BTC for 2000 EUR in 2021
Without grouping, you will have a profit of 1000 EUR in 2020 and 500 EUR in 2021
With grouping you will have an average of 1250 EUR and thus a profit of 750 EUR in 2020 and also in 2021.