I appreciate your situation.
Every now & then I try to slip in some humour, some times it works & some times it don't
A little jest is always better than a plain RTFM.
There is only one brake on a mower, that is all there is to stop you or stop it running way when your back is turned.
Very few people have the presence of mind when chasing run away mower to reach across and turn the key off, or grab the wheel the steer it up hill .
They attempt to mount the moving mower, usually end up putting their foot on the deck which gives way cause it is floating then they fall backwards and get run over or fall foreward and smack themselves hard on the wheel, seat, levers etc.
Either case is not pretty, lost a customer who ended up loosing a leg doing exactly that.
The single section of the manual that Engine man posted dose not cover readjusting the clutch nor give any detail as to why the brake might need to be adjusted,
In 5 years as a mower mechnaic the only brakes I have adjusted all needed backing off or just dissasembly and cleaning, they very rarely wear out because you can not drive with one foot on the brake and the other on the throttle.
The section that was presented to you also makes no mention of belt damage.
There was also no parts breakdown.
All this is in the manual and should be read & understood before some one with no experience starts to fiddle with the brake.
It is a simple device but very easy to get totally wrong.
Lastly you did not mention why you wanted to adjust the brake.
Nearly every time I have been asked to adjust the brake it was not the brake that needed adjusting, it was the clutch.
While the 0.010" is a good starting point to avoid whiplash whenever you release the the clutch /brake pedal many times the brake needs to be set differently to avoid the clutch & brake fighting against each other.