Hi they are the amount of drive cycles stored after the fault, so as I said delete the codes as most of them are a one off and old, I would think your code storage must be about full as the counter numbers in theory should go down with each cycle within which the fault has not re occurred unless the memory is nearly full in which case they will remain stored with the original allocation number 255/40, therefore I cannot overstate the value of a once monthly scan and clearance of one time codes this will also give you a heads up with a failing component before it goes bang and ruins something else especially things like oxygen sensors, mine was occasionally throwing a fault but no EML so after I cleared it it reappeared a week later which was all I needed to be convinced replacement was the best option I could have just carried on clearing it until the thing failed completely and the car won't do any regeneration of the DPF therefore blocking it, timely replacement stops this happening along with a horrendous bill for a new DPF.
Steve.