It depends. If the auto PB system already placed the PB day from the original award on the LC day then you’ll still get full pay above guarantee. If that is the case then consider yourself lucky. In reality in that case you’re only supposed to get day A paid above guarantee and all of day B + trip credit would go towards reserve guarantee.

The other question is were you delayed or actually rerouted? A delay incurs no form of reroute pay. A reroute of any sort will generate L4 pay. Again in theory you shouldn’t be due L9 pay for a reroute because you weren’t rerouted into a day off. But if the PB day is there you may still get it and again if you do consider that a win.