Speedometer Correct but Odometer Wrong after bigger tires??

I just got a set of Toyo ATIIIs in 265/75r16 and I was expecting to need to recalibrate my Speedo and odometer but I’m seeing some weird results. First of all the tires have a stated height of 31.7" but when I measured them once installed they are only about 30.5" in the front and a little shorter in the back (probably due to weight in the bed). I know they are often a little shorter than stated, but I wasn't expecting this much of a difference.

Additionally, what is more, concerning is the speedometer seems spot on but the odometer is a little off. I never really paid attention to the speedometer and odometer readings with the original tires because I just assumed everything was correct. But I was comparing it with a GPS to see how far everything was off and noticed the speedometer is pretty spot on. Once I get up to like 80 mph the speedometer reads maybe 1mph slower than the GPS on my phone (I used several apps to check). However, my drive home from work is about 9.5 miles and two apps on my phone showed 9.4 miles and the odometer only clocked 9 miles. I'm very confused about why one seems right and not the other.

I bought the module from Hypertech expecting to have to recalibrate it, but now I'm not sure what to do. Anyone else with similar experience or suggestions?