The numbers by the book: New 25mm thick, Wear Limit 22.0mm, Wear Limit for maintenance service 22.6mm.
I presume the difference between the two wear limits infers that if pads are necessary and the limit is below 22.6 then one should replace. if the pads are alright then nothing is necessary till 22.0mm.
This is for chassis 202.028 after 9/95 without option Code 956 AMG package. With the AMG discs the numbers are 30, 28, 28.5.
Bosch Master, ASE Master, L1
33 years MB technician