speedometer adjusting

[HioSSilver]

I have done it before, alog with other tuning but I can't get it to change now. What am I over looking? I type in the diameter and click the button next to it and it changes the trans values but the the tire diameter won't change. I'm working on a 03 2500hd. Trying to change from 32.5 to 31.9 cause' my speedo seems a little fast.

[SSpdDmon]

Enter your values, click the circular arrows, click the Adjust button, accept the trans settings (for MPH ref'd tables), and then click the Save button to update the settings in the cells below (pulses per mile, trans output, etc.). If the trans is set already...just click the Save button to update the cells below.

[HioSSilver]

I have did that several times and it won't change. I did a fresh download after I tried to reprogram it and it still read 32.5. It will alter shift points though and save all that stuff. It just won't change the speedo tire size. More help please.