The reason why they were enumerated here once again seems to be because this is where the text begins to recount the story of the enslavement of Israel - so that a person will not consider saying that it was because they were, heaven forbid, not respectable as a result of the troubles they went through during enslavement. Therefore the text counts them again, to show that they are important and beloved. Their number indicates their importance; one should not think that they were exiled because of their transgressions.