How did the Stoics define exclusive disjunction?

The Stoics defined an exclusive disjunction as a compound proposition that is true if and only if exactly one of its constituent disjuncts is true.1

While the Stoics were also aware of inclusive disjunction—which is true when at least one disjunct is true—they favored the exclusive interpretation in their logical framework. This definition was central to their development of propositional logic, where they utilized ordinal numerals as variables to represent whole propositions in schematic arguments, such as: "Either the first or the second; but not the second; therefore, the first".1