Call this a lore dump, I guess; I slapped together a quick picture to illustrate 1: how big Eila really is and 2: how much space 500 rooms takes. Yes, this was really effortless, I made one quick mockup room and used three Array modifiers to make the rest.

Most of the hybrids live in pairs of two, whether they like it or not, which means they need about 500 housing units. Some hybrids are small enough to justify there being more than two per room, and some hybrids are big enough that they get one big room to themselves, but it still ends up being around 500 rooms.

Each living area is built roughly in the same size and design as an average American studio apartment, minus the kitchen: One living area with place(s) to sleep, a full bathroom and a closet.
Food, drink and fun are held in other parts of the lab, probably as a means to get the hybrids to interact more, and to avoid having to build 500-ish kitchens and such.

The only room out of all 500-ish that /really/ stands out differently is Lyyona's room, since she basically runs an orphanage, taking care of the 10 or so kid hybrids in the lab as their adoptive mother. Her room is the size of about three or four normal rooms, and DOES include a little kitchen, plus an extra half-bathroom.