https://youtube.com/shorts/ojaFiIGSPrA
I have Goose purple at 4 covers, which means each tile reduces damage by 24%. You can see my Goose has taken almost no damage and there are currently 4 Kitty Cat tiles on the board.
When the final tick from the enemy OR drops he goes from 64,693 to 47,385hp.
Funnily enough, the "damage number" shown on the character DOES show "-1"... (when in reality it was -17,308 )