Updated Usage (markdown)

Usage.md

@@ -209,4 +209,12 @@ To scan the same TCP and UDP port, but also scan specific TCP and/or UDP ports,
 
 ```
 autorecon --ports 53,T:80,443,U:123,B:88
-```
+```
+
+## Max Scans
+
+Since AutoRecon is multi-threaded, it can launch multiple scans against multiple targets. The max scans option controls how many scans can be running at any one time. Each plugin which runs a command is counted as 1 scan towards the maximum. This is important to know, since some of the tools used by the scan are also multi-threaded. For example, the ServiceScan plugin "DirBuster" runs directory busting tools like feroxbuster or gobuster with 10 threads each, however each instance of the plugin only counts as 1 scan rather the 10.
+
+To prevent AutoRecon from port scanning too many targets at once and using up all scans, the number of scans reserved for PortScan plugins is calculated as 20% of the max. By default, the maximum number of scans is 50, so 10 are reserved for PortScans, with the other 40 reserved for ServiceScans. Note that when there are no more targets to port scan, AutoRecon will allow remaining ServiceScan plugins to use scans reserved for PortScans plugins.
+
+The `-m` and `--max-scans` command line option controls the maximum number of scans AutoRecon should be running at any time. It must be at least one, and cannot be more than the max-port-scans value (but can be equal to it).