Rule 356.4.e

If a discount applies a minimum cost, that minimum applies only to that discount. Example: Eager Apprentice says "While I'm at a battlefield, the Energy costs for spells you play is reduced by [1], to a minimum of [1]." A player who controls Eager Apprentice and a unit with 7 Might plays Sky Splitter, a spell that costs 8 Energy and says "This spell's Energy cost is reduced by the highest Might among units you control." That player can choose to apply Eager Apprentice's discount first, reducing Sky Splitter's Energy cost to 7, then apply Sky Splitter's discount, reducing its Energy cost to 0. If they applied these discounts in the other order, Sky Splitter's Energy cost would be 1.