@kaminomikan Actually, while the translation is a bit iffy there, I think it meant to say that you can't get the same skill two days in a row, so that the current skillset will always be completely different everyday. The skills themselves will still be potentially usable again two days later.
Though that also contradicts the anime a bit, since he implies there that, while the possibility of him getting the skill is random, there's still the possibility of him getting it again the next day. Granted, continuity errors, or outright story changes, between the manga and anime adaptations of light novels is nothing really new, so the anime might be a lot more accurate to how it works.