The OBD2 system is a vehicle emissions control system that is required on all vehicles sold in the United States since 1996. The system monitors the vehicle's emissions and stores DTCs when it detects a problem. These DTCs can be read with a scan tool, which is a device that can be plugged into the vehicle's diagnostic port.
The since DTCs cleared vs last drive cycle value can be found on the vehicle's scan tool. It will typically be expressed in miles or kilometers. The higher the value, the longer it has been since the DTCs were cleared.
If the since DTCs cleared vs last drive cycle value is high, it is possible that the problem that caused the DTCs to be set has been fixed. However, it is also possible that the problem is still present and has not yet caused the DTCs to be set again.
If you are concerned about a problem with your vehicle, it is important to have the vehicle diagnosed by a qualified mechanic. The mechanic will be able to use the OBD2 system to retrieve the DTCs and diagnose the problem.