Measurements of rooftop awning area?

Hi all, I wonder if you can help me.

I wondered if anyone knew the measurement of the section on the top floor apartments where the sun shades are fitted? I’m trying to get a quote for a sun shade for the rooftop apartment I’m purchasing on N2. 

Thank you in advance and see photo of the bit I’m referring to as I don’t know what to call it, sorry.

Lorraine