1st floor: an illusionary copy of all other business buildings, with a reception desk (Susan's) and an elevator past the far hall. The elevator can only be accessed with a key card and pin number, which all characters have.
B1 floor: Medical station
2-5th floors: also illusionary office building floors
6th floor: Combat practise floor 1, melee weapons training specifically. There's different rooms with holographic dummies to train with just about any sort of melee weapon.
7th floor: Combat practise floor 2, weapons training with guns, specifically. Of note, the entire floor is soundproofed, so gunshots can't be heard outside of this floor.
8th floor: Combat practise floor 3, weapons training with alternate ranged weapons.
9th floor: Supernatural practise floor. This is usually where Rituals or other Crafts can be practised.
10th floor: Laboratory 1. The entire floor is essentially a lab to make various electronic equipment. Sarah often works here.
11th floor: Laboratory 2. This floor is dedicated to the crafting of more material objects, such as guns, or even blades.
12th floor: Laboratory 3. This floor is dedicated to chemistry.
13th floor: conference and office floor. The conference room is located on the northern side of the building, while Mr. Kurosawa's office is on the eastern side. The character's don't have their own rooms, but instead share a spacious room with multiple computer terminals. It's designed this way so that it's easy to converse and work with each other. Sarah's terminal, where she usually is, is also located here. It's easy to see which computer hers is, since it's so rigged with so many external hard drives and other devices that there's hardly any other room on her desk.
14th floor: Medical station.
15th floor: Unknown. Not even Mr. Kurosawa has access to this floor. Presumably, it's "A's" office.
And that's all the relevant floors I can think of offhand... although there are more... it IS a skyscraper after all