If an odd damage roll is halved and then doubled, does it result in the same value as before, or one less?
Let's say there's a Dust Mephit at full health that was hit by the Fireball spell and made the save. The damage on the die is low at 17, so the fire damage is halved. But, Dust Mephits are vulnerable to fire damage, so it's doubled again. Does the rounding happen after the final total, and it stays at 17? Or does rounding down happen after each step, reducing it to 8, then double to 16?