Me thinks that 6400ft refers to the 'useable' distances rather than the length of the concrete!
Declared distances for take-off, landing, emergency etc often bear little resemblance to the physical dimensions of a runway. Granted the runway 14 Take off distance [as opposed to the Take-off run] far exceeds 6400ft, but its about right for the remainder of the LBA declared distances.
Perhaps the 700ft airfield elevation is a euphemism for a long way up [especially when the cloud base is down at Pool]!
H49