Reference
Description
The third floor was the third story of a building, that is, the second floor above ground level, which is “second story” in British usage and “third story” in American usage.
Translation
Translators should be careful when expressing what happened to Eutychus in ACT 20:9. While some languages will designate the room from which he fell as the “second floor,” they may have to say that he fell “three floors.” When designating the location of the floor, it would be called the second, but the distance he fell includes also the ground floor, so he fell three floors.