The highest number assigned to a slot in the system. In a particular
hardware model, module slots have fixed numbers assigned to them, even
though in some instances there may be no actual slots associated with a
particular number. In all cases there is a maximum slot number that
will never be exceeded:
2 for ERX-3xx models
6 for ERX-7xx models
13 for ERX-14xx models
16 for E320 models
Note that slot numbers are zero-based.