[cl-opengl-devel] gl-array count

I've been slowly getting my head round the gl-array macros and there is one last thing that is confusing me In this struct, size is set to the type of unsigned byte...why? It seem that this stores the length of the foreign array which, as far as I can tell from CFFI doco, is an integer.

(defstruct (gl-array (:copier nil))

"Pointer to C array with size and type information attached."

(pointer (null-pointer))

(size 0 :type unsigned-byte)

(type nil :type symbol))

There's probably something I'm missing and if anyone can explain that would be great! Thanks folks