Jb hunt idle policy

Do you know the formula Swift uses to calculate idle %? I've been with Swift for several months now and recently got a message and phone call about my idle %. The truck I have doesn't have an Opti-idle feature. I pretty much said F-it after seeing I didn't hit the fuel bonus for two months when I was mostly up North and I was leaving the truck off when I slept.

Recently my DL sent me a screen shot (IDs blurred) of his excel sheet sorted by idle % highest to lowest, and split up by week. On the sheet for the weeks I was sleeping with the truck off my percent was still "high". After seeing that my inclination is not to trouble myself too much over it.