Further clarification on --max-cpus

Emphasis on each process, not the overall nextflow submission.

Author: jfy133

docs/usage.md

@@ -237,7 +237,7 @@ Use to set a top-limit for the default time requirement for each process.
 Should be a string in the format integer-unit. eg. `--max_time '2.h'`. If not specified, will be taken from the configuration in the `-profile` flag.
 
 ### `--max_cpus`
-Use to set a top-limit for the default CPU requirement for each process.
+Use to set a top-limit for the default CPU requirement for each **process**. This is not the maximum number of CPUs that can be used for the whole pipeline, but the maximum number of CPUs each program can use for each program submission (known as a process).
 Should be a string in the format integer-unit. eg. `--max_cpus 1`. If not specified, will be taken from the configuration in the `-profile` flag.
 
 ### `--email`