Here is the state code:
41-6a-606.
The definitions of speed contest or exhibition of speed are vague which gives latitude on what would apply. I think accelerating hard from a stop *could* apply though as a demonstration of speed. Notice though on the bottom of that link the penalties. For the first offense you lose your license for 60 days, that is the biggest place it'd hurt you. The fine is $500 plus 35% surcharge ($175) and then potentially additional city court fees (up to about $50.) So you're looking at at least $675 and 6 months without a drivers license for a penalty.
It will get reported to the drivers license division and that will hit on your insurance which will drive your regular vehicle insurance rates up as well.
(The code I linked was updated or listed effective May 2017 and the bail schedule was as of April 2017 so they are both current.)
I'm guessing your attitude while talking to him, the fact you had your papers together, and perhaps that you didn't go above the speed limit all were taken into account when he was deciding on whether to give a citation. I wouldn't assume you'll be so lucky next time.
