Hi,
The brake pedal you mention is not actually a brake pedal that applies brakes. It is call an inching pedal. What it does is stop the oil being pumped to drive the wheels. This allow the truck to slow down to a stop. Some trucks are fitted with a button below the inching pedal that will apply the brakes after a pre set no of seconds as you do not want the truck to suddently stop if carrying a high load.
This is explained in the manual that should be in the truck.
I hope this helps, but if you need additional help you can submit a support request via the combilift web site, www.combilift.com and just scroll to the bottom and select "Technical Support". There is no cost for this support and no login required.

Hope this helps
Richard