how can i adjust room area shown from no. 1 to no. 2 without errors? is this possible?
Adjust the limits, like it is suggesting?
You can work with Room Seperation Lines.
Revit Rooms will automatically be truncated vertically by Room Bounding elements (Floors, Ceilings, Roofs)- just use the triangular grips (in section) to override this and set their height manually.

Delete the room and place it again.
Make sure to Go into visibility/graphics - lines and show room separation lines.
You do this to make sure the room is place correctly.
If the room still is not right. You could place a room separation line yourself.
Lastly check that the floor/wall is set to Room Bounding!
Best Regards
P.S. (you could also try the add-in "Room Finishing" https://apps.autodesk.com/RVT/en/Detail/Index?id=5641957956279354474&appLang=en&os=Win64)
Sie finden nicht, was Sie suchen? Fragen Sie die Community oder teilen Sie Ihr Wissen mit anderen.