Thank you both for taking the trouble to reply. My apologies for not expressing my question more clearly. I will have another go:

Statement 1: the box contains a horse or a donkey or a cow
Statement 2: the box contains a horse or a donkey or a unicorn

On the basis that the box contains a horse, both statements are true.

But the presence of an impossible item in statement 2 gives it a different status from statement 1. Is there some conventional terminology that is used to distinguish the different statuses of the two statements?