So those change in number of coins aren't related to the consensus rule?
No, since this is an external measure.
Something similar would be "BTC that are not held by Bitstamp". This number is likely to change over time, but doesn't have anything to do with the total number of BTC or consensus rules that have to be respected by miners (e.g. <=50/25/12.5 ... BTC per coinbase transaction).
Coinmarketcap.com just chose to only display the portion of any currency that is
not held by the creators/custodians of that currency, see
https://coinmarketcap.com/currencies/views/market-cap-by-total-supply/ for the actually existing numbers of tokens for each currency listed there. This number is the one that is enforced by consensus rules and which can only go down.