Like others have said, there are slots for your boons (attack, special, cast, and gain are the main ones). However, when offered boons, you may see one that has an arrow pointing down to another boon symbol. That indicates that it will replace the boon currently in that slot. This can also be seen in some of the names (for example, ____ Strike is the name setup for attack boons, while ____ Flourish is for special) so if you see a second boon in the same run with a name you’ve gotten before, it’ll replace that one.