The pushrod of the brake booster that engage the master cylinder is held to the brake pedal by a cam (eccentric)bolt.



Per Chilton manual:
"The brake pedаl travel should be 6.08" on all (dual circuit) models. To adjust on all models (except 230SL), turn adjusting bolt (the cam bolt) until the notch on the bolt head points rearwards.This gives maximum travel, and adjystment is made from that point.
NOTE: If If pedal hits brass thread of brake light switch, use shims under switch so that switch button protrudes 0.16" .

The above may be wrong on the total pedal travel ...however you need to make sure that there is some pedal freeplay before master cylinder engagement (by changing the position of the cam bolt).