Days turn into weeks.
Ruby finds his knowledge to have... weird gaps. A weird shape. He seems to have exceptional control over his own magicka, the kind of control that would typically require years of practice, but when it comes to individual spells he seems sorely lacking. Not in a comprehensive or reliable way, though; it's hard to predict what he does or does not know. He seems to have some basic grasp of the more general forms of elemental magic, but not of individual specialised elemental spells, especially ones typically associated with the Destruction school of magic; similarly for Regeneration, he can do some basic self-healing and some wards but nothing very complex. He seems to know no individual Illusion spells, but to have a more holistic kind of understanding of the discipline that coupled with his control means he can easily keep up with the more knowledgeable Apprentices. And when it comes to Alteration and Conjuration, he does seem to have more of an understanding of discrete spells, but once again which exactly they are is kind of unpredictable.
Beyond magic, he does not seem to be acquiring any further memories. It seems he only recovers them when he runs into a sufficiently close association, and he's pretty sure now that whoever he used to be just did not live anywhere near the College or the city of Winterhold.
He and Onmund eventually get used to the complete lack of a taboo around nudity and sexuality, him more quickly than Onmund. The two of them become regular fuckbuddies, and one could say they're even dating, save for how Ruby is not inclined to be monogamous and takes a more anarchical view of relationships. Brelyna and J'zargo are both "occasionally, when they feel like it" situations. It turns out khajiit dicks do have barbs which—coupled with magical healing and painkilling—does make for a very interesting experience which it seems neither Brelyna nor Onmund are interested in experiencing.