What does A5 service mean on a 2011 glk 350

It's an A level service (oil change and filter, general check over, check your maintenance book to be sure) **Service A Repairs: Mercedes-Benz Synthetic Motor Oil Replacement^ Oil Filter Replacement^ Brake fluid level inspection Brake linings inspection Windshield washer system check Service indicator reset The 5 could mean extra service dictated by age or miles only... here's the list I know of... Service item 1 means an ‘A’ service Service item 2 means ‘B’ service. Service Item 3 is due on every service as it is engine oil and filter change. Service 4 – Brake fluid change Service 8 – Air filter replacement. Sometimes diff oil (check service sheet) Service 10 – Sunroof guide rails clean / regrease Service 11 – Fuel filter replacement Service 12 – Replace spark plugs Service 13 – Engine coolant renewal Service 15 – Towing hitch lubrication Service 20 – Gearbox oil change / filter renewal Service 24 – Cambelt replacement / Waterpump replace But I have no idea what the "5" stands for.... ,