fmd The channel IDs don’t need to represent the number of channels in the plant
Channel ID’s should always be treated as opaque numbers, with no meaning.
The DOCSIS channel IDs (internal DOCSIS channel IDs, what your modem displays may be different) need to have no association with anything (other than they need to be unique). They could start at 1, or 13, or 200, no matter how many channels are being used. They also do not need to be sequential (channel IDs 15, 22, 23, 55 could be in the config). In the (bad) old days, the channel ID may have had an association with the physical card port in a CMTS. In more modern (v)CMTS’ the numbers can be assigned (mostly) arbitrarily, and most of the automation tools (and all proper engineered operators use automation tools) will tend to choose to start at 1 and go up for new configurations (but remember that to avoid operational impact, existing channels (and their IDs) may be maintained even as other channels may get added/shuffled).
If you want to know what your plant is actually configured to do you are going to need access to much better tools than a modem (I would prefer the (v)CMTS config, but no operator shares those publicly).
