How does Simic Hybrid's Manta Glide work?

Question

Simic Hybrid's Manta Glide (GGR p. 20) states the following:

You have ray-like fins that you can use as wings to slow your fall or allow you to glide. When you fall and aren't incapacitated, you can subtract up to 100 feet from the fall when calculating falling damage, and you can move up to 2 feet horizontally for every 1 foot you descend.

When you fall, do you subtract up to 100 feet from the fall distance or the fall damage calculation afterwards (10d6 falling damage)? Both are part of the calculation of fall damage so which step does it apply to?

The first interpretation means that this trait will not have any effect on a fall that is greater than 300 feet because falling damage caps at 200 feet (20d6) whereas the second interpretation will always allow you to subtract 10d6 falling damage from a fall of any height.

Answer 1

Subtract the distance

Your first interpretation would be the correct one as the text says you subtract 100 feet from your fall. It doesn't refer to the damage roll at all unlike the slow fall ability of the monk class.

Answer 2

The rule for falling damage says,

At the end of a fall, a creature takes 1d6 bludgeoning damage for every 10 feet it fell, to a maximum of 20d6.

Since this ability lets you "subtract up to 100 feet from the fall", you're reducing the "for every 10 feet" component.

In other words, you subtract 100 from the distance fallen first, then from the remaining distance fallen, you calculate your impact damage. At 300 feet or more, you still take the maximum 20d6 damage, but below that level, you're still getting a benefit from your glide (and you can still gain forward movement from the entire fall, no matter how long it is, if that helps any).