Refer to this thread for more things you need to watch out.
Home Defect Rectification Checklist, After vacant posession! Update With Pics
As for your question. Hire a professional to do the measurements. Only certified professional can declare it is according to floor plan or not. If you want to sue the developers.

The floor plan can be confusing if you don't understand. There are two main convention with regards to floor plan. So you may misread the floor plan as well.

Post the floor plan, then post a picture showing the measurements, and how you measure it.