The Ledgerdemain Lounge is the upstairs area of the Legerdemain Lounge in Dalaran. It is here Afsaneh Asrar, the assistant innkeeper, resides. Below is the tavern part of the lounge with innkeeper Amisi Azuregaze next to the stairs which lead to the bedrooms.
Although Afsaneh is an assistant, she acts like a full fledged innkeeper. When your hearthstone is set to her you will appear here on the second floor, this could be the reason why this subzone was named differently.