About ADP170/1 thermal consideration

Hi,

I have a question about thermal consideration on ADP171 datasheet.

http://www.analog.com/static/imported-files/data_sheets/ADP170_171.pdf

According to Table 6, there is θja for each copper size.

Does this GND copper area means the surface layer or it's also including other layer such as 2nd(whole GND)layer?

For ADP170 evaluation board, what are the GND copper size and θja will be?

Best,

Tarzan