A colon (':') separates the subsystems. The subsystems which follow the colon are on a lower level. For example, in command:
:SOURce:POWer:STARt
the start power STARt is a part of the POWer subsystem, which is a part of the SOURce subsystem. The stop power is also a part of the :SOURce:POWer subsystem. It is specified by:
:SOURce:POWer:STOP
The first colon in the line can be omitted, for example:
SOURce:POWer:STOP
Rev.: 22.3