Speeodometer readings and OEM wheel options
 

The sport package comes standard with 255/50-19s. The 20" wheel option (275F/315R) actually gives you a slightly smaller circumference, and the speedometer would then be off by 1.3% compared to the 19" setup.
Is there a factory setting / adjustment I can make to the odometer to compensate for the smaller circumference if I decided to upgrade the wheel package?

No adjustment. 1.3% will not make a difference that you could notice. Given that the speed registered by the odometer is 5.0 KM/H slower than the actual speed. I tested this against my GPS and the speedometer is consistently 5 KM/H slower than what the GPS speed reading is when traveling above 25 km/H.

I would think Denalio is right. Probably not a significant difference worth worrying about.

Does anyone get speedometers recalibrated anymore?

By the way, how accurate are typical portable GPS speed readings?

use this tire calculator to see if you can find a spec closer to original. I agree 1% means nothing and you will never notice it...

Tire Size Calculator - tire & wheel plus sizing