Mk III max burst speed

Forget it - I've discovered what I was doing wrong ...........

Regardless of image size and ISO chosen, my camera always shows 14 as the max photos per burst, on right side of viewfinder, above JPEG.

Thinking the viewfinder info might be wrong/stuck, I tested the burst rate, at an exposure time of 1/1000, using a Sandisk Ultra IV 8GB CompactFlash card, at image sizes of L and S (no RAW). At both sizes, the camera managed only 24 frames before hesitating. The manual gives 110 and 160 as the approx max burst - so both the viewfinder info and the actual rate are way out of spec.

I can find no pointer in the manual to this problem. Can anyone help me? What am I doing wrong?