From my experience so far, I have never exceeded 76 percent, so never seen this message. If you do city driving for weeks on end, then chances are you never meet the criteria for a REGEN. I find, that one need to maintain an rpm of 1500 to 1800. (One way to do that, is downshift to lower gear, using the minus gear button). Also, you need EGT temps (about 1000 to 1250 F) to last for several minutes. If it only happens for a few minutes, then your soot will not drop down to 9% or less but anywhere from 24 to 40%, which is okay. When the soot hit over about 65%, the process will repeat.
I suspect, if you interrupt your REGEN often enough, you may see more use of DEF used (cheap). I have about 8k and I'm still around 60 percent full. One should have no problem getting 10k before you need to top off. Due to shelf life, I don't plan to refill until I get down to 25 percent. Keep it fresh. Apparently the vehicle will give a message when you are low and if you refill and it bad, it will tell you to replace. We have smart phones, now we have smart trucks. LOL. The answer, not to worry, just go for a drive and drive with RPM at least 1800 or more steady and it will clear up in 20 km or so.
Here is what Manufacture says:
Under certain conditions, your diesel engine and exhaust after-treatment system may never reach the conditions required to remove the trapped particulate matter. If this occurs, the “Exhaust System — Regeneration Required Now” message will be displayed on the EVIC/DID screen in your cluster and you will hear one chime to alert you of this condition. Driving your vehicle at highway speeds for as little as 45 minutes can remedy the condition and allow the engine and exhaust after-treatment system to remove the trapped particulate matter.
NOTE:
Under typical operating conditions, NO indications of regeneration state will be displayed. If you do reach 80% of filter capacity, the following messages will assist you in inducing and understanding the regeneration process.