Canon EOS-1D X Mark II DSLR Camera (Body Only) - Manual (Page 232)

s : Shutter-Priority AE
232
If the lowest f/number blinks, it indicates
underexposure.
Turn the <
6 > dial to set a slower shutter speed
until the aperture stops blinking or set a higher
ISO speed.
If the highest f/number blinks, it indicates
overexposure.
Turn the <
6 > dial to set a faster shutter speed
until the aperture stops blinking or set a lower ISO
speed.
Shutter Speed Display
The shutter speeds from “ 8000 ” to “ 4 ” indicate the denominator of the
fractional shutter speed. For example, “ 125 ” indicates 1/125 sec., “ 0"5 ”
indicates 0.5 sec. and “ 15" ” is 15 sec.