N/T means No Time. That’s for the shit talkers who don’t want you to know what they run. Often the 4X number stickers are the drivers NHRA permanent Competition number and will start with the NHRA division number. I’m my case it’s a 7. That indicates the Pacific Division. Mine is 7027. Other sanctions have their own numbers for identification purposes. If I were to run MSHS my number is 960. I ran one of their events once and was assigned that permanent number. For most open events, you just pick one so they have it for your time slip.