Wizard Flight Spell Question

[topdawg95jd]

The card states that you may play cards to increase your chances of escape AFTER rolling. How exactly does this work?

Does this mean if you, say, roll a 2 on the dice you would need to discard 3 cards to cover numbers 4, 3, and 2 (since 5 and 6 are automatically covered) where if you rolled a 4 on the dice you would only need to discard 1 card to just cover the 4.

I cannot wrap my head around how retroactively adding increased chances at escape would work after roll.