 To illustrate the difference, recall that it is a convention of English that a speaker uses “I” to refer to themselves. That convention is available to us, roughly speaking, whenever we are conversing with fellow English speakers, and we must always disambiguate an uttered token of “I” (distinguishing it, say, from homophone “eye”) prior to applying this convention to determine the token’s referent. The availability of the “I” convention in a conversation, and the disambiguation of an individual token of “I”, while crucial to communication, are matters that come before applying its rule of use, and so are distinct from the matters addressed in that rule.