I think that the text is from a report on the condition of a vehicle by a mechanic. There are too many abbreviations for any non-specialist to be able to make sense of it.

Intermediate in GDL - GDL stands for Graduated Driver Licensing. You can be in a Learner Stage, Intermediate Stage and Full Privilege Stage. For every stage there are some implicit restrictions to drive a vehicle (age, time of the day, number of passengers). Air brake not auth - I assume it means you are not authorized to operate a vehicle that has a full air brake. Stage f effective - The 'Stage f' is a reference to the Full Stage from GDL 0 BAC end-CIs 1 to 5 - BAC stands for Blood Alcohol Concentracion. The 0 means that there is an upper limit of 0 BAC for the classes 1 to 5 (Different types of vehicles are assigned to different classes. For example, class 6 is for motorcycles). Elig to supervise Cls 5 - Means that you are eligible to supervise class 5 which is passenger vehicles and light trucks.