How does Doomfist's "The Best Defense" Passive work?

Each enemy hit by Doomfist's abilities (including Rocket Punch) generates 30 shields if hit by a regular ability, and 75 if hit by Meteor Strike, up to a maximum of 150 extra shields. The amount of shields generated does not depend on how much damage Doomfist deals with his abilities.

These shields are temporary and will disappear when damaged; starting one second after they were gained, they will start decaying at a rate of 3 shields per second.