Old School RuneScape uses the British convention for floor numbering: Ground floor, first floor, etc.
Premade choc s'dy detail

A premade choc s'dy is a drink that can be bought at Blurberry's Bar in the south-east corner of the 1st floor[?] of the Grand Tree. Premade drinks cannot be used in the Gnome Restaurant minigame.

Drinking it heals 5 hitpoints and temporarily adds +6 to strength while reducing attack by 4.