INCREASING 02 STORAGE B2 to Pass Emissions

For the first time my 2006 Prius with 177k miles failed an emissions test . P0420 and P0A93-346 were the culprits. Brought it to a mechanic who told me P0420 "almost always" means a catalytic converter replacement. So I got it replaced, along with the water inverter cooler pump.

Check engine light off for a while - until it wasn't.

Did some digging around - frankly not knowing exactly what I was looking for - and found "O2 Storage B1" as the notable designated failure. Test value of 0.004 (no units) with min and max of 0.019 and 9.993, respectively (little confused how the reported "Min" was 0.019 with a "Test Value" of 0.004 - wouldn't 0.004 be the min?).

Anyway, the cat I purchased came with an 02 sensor, which the mechanic said he was going to install. I've looked over the TIS tech process for the Toyota Official "P0420 Inspection Procedure" and didn't see anything about changing the 02 sensor, other than "the Oxygen Storage Capacity (OSC) in the catalyst [is] based on the voltage output of the sensor 2."

Perhaps the O2 sensor could be sending faulty info for the OSC calc, thereby triggering the error? I don't know.
Question: What needs to be done to increase 02 Storage B2?

Any guidance, as always, would be greatly appreciated!