One might think this is the general way to understand counting sentences in ordinary language. So There is exactly one F gets interpreted as There is an F, and no F is wholly distinct from it; and There are exactly two Fs gets interpreted as There are wholly distinct things x and y that are both F, and no F is wholly distinct from both of them, and so on. We can either take this to be a formal explication of Lewis's talk about almost identity, or a new proposal; it's hard to see what would tell between those interpretations.