5.514 If a notation has been set down, then there is in it a rule according to which all propositions negating p are to be constructed, a rule according to which all propositions affirming p are to be constructed, a rule according to which all propositions affirming p or q are to be constructed, and so on. These rules are equivalent to the symbols and in them their sense is mirrored.

More on rules. So symbols and rules are equivalent, and both depend on the notation. Although every notation, to be a notation I suppose, necessarily has these rules.