How to choose surfboard socks?

• Sock size: 6'0"------suitable for board size: 5'6"-6'6"; (Full Size: 187cm*50cm, Point Nose)
• Sock size: 9'6"------suitable for board size: 8'6"-9'6" (Full Size: 302cm*55cm, Round Nose) 

        (*Please allow slight dimension difference(1-3cm) due to different manual measurement.)