Hi there Dori.  This happens when we're trying to make it clearer that your answer matches a "model" answer (or reduces the differences that aren't significant).  In "free text" responses we try to make sure that everyone's answer is checked in a way that doesn't penalise you for trivial differences (or errors that are not material to the question).  I would need to check the specific case to explain in more detail, do you recall the question that this happened in specifically?