CBS keps delaying my 1st service
 

For quite some time, CBS (Condition-Based Service) indicator suggested that I should get my first service around 15K miles. I am almost at this mark and CBS is now telling me that the vehicle will be due for service by 24K miles. What a change!

But I am still bringing it in for an annual oil change tomorrow.

the dealer can see your anniversary date and they just go by that, no need for the vehicle to mark the date.

I seem to recall my service interval did something similar to what you described. I just brought it in for service around 15k and told them and they fixed it - don't recall if it required a full software redo or what.