The concept of a mind is not the same as an instance of a particular mind, any more than a algorithm is the same as a running process, or the idea of 3 is the same as a set of logic gates designed to represent a 3 in binary.
Mistaking our own internal representation of our own mind (our consciousness) for our actual mind is what Dennit is arguing against.
What question? It seems pretty clear what they are saying: the concept of mind is a social contruct, metaphorical, a figure of speech rather than a figure of physical reality.
Mistaking our own internal representation of our own mind (our consciousness) for our actual mind is what Dennit is arguing against.