Franz can't keep the score

Void-touched Hound starts with 42 HP. Maeryn does 6 damage. I roll another 6, but Franz doesn’t realize I also have Sneak Attack active. I prompt him, he brings up the Roll button. I roll for 4. Something bugs, Franz has a “you were saying?“ moment, I tell him I was asking about the sneak attack, he instantly deducts another 11 HP from the hound. I ask him to review the encounter because something is off, he deducts 3 more HP. I tell him his math is off, he keeps deducting HP, hound’s almost dead