If you are grabbing the stats from swgoh.gg, I think the site is bugged right now to show the Resistance Penetration for special damage. All Boba's attacks are physical damage though.
My Boba has 103 (flat) armor penetration for physical, and I only have the g12 piece that gives +60, and not the g12+ one that gives +100. With all pieces he will have 203, so after his payout he will have 609. That's flat.
If your Boba is under g12, I would look at the armor penetration under physical damage to see how much it is.