I noticed that my manuals are very old in my system although all updates done.
man cmp tells about the flag
-l --verbose Output byte numbers and values of all differing bytes.
while Wikipedia is about more fully
Output the (decimal) byte numbers and (octal) values of all differing bytes, instead of the default standard output. Also, output the EOF message if one file is shorter than the other.
The last sentence was critical in my understanding of the output. I would like get more fully manuals to my system.
Possible ways to get better manuals
How can you install better manuals to your terminal commands in OSX?