I am sorry to respond here, I am not qualified to advise anything, but I am interested in the answer - I did this job on my car and would like to make sure I did it right.
I do not have my BBB at hand, but from the instructions I translated for my mechanic from BBB, I have that the bolts marked "a" (which is what I think you are referring to) on the picture we use the torque of 25Nm.
Is this correct?