I’ve just realised that this card (Interrupt: When boost icons on an encounter card are counted, exhaust Scarlet Witch's Crest → increase or decrease the number of boost icons on that card by 1 for this count.), when resolved on a card that has no boost icons, allows reducing the count to -1. So, for example, it allows decreasing the villan’s attack by 1.
Is that intentional? Surely that can’t be the original intent of the card?