ARM Cortex-A17 clock speed specification.

Hi there, I am quite new to this. I bought signage with CPU 4xARM Cortex-A17 and the problem was the specification said it has 1.8GHz ,but when I checked it has only 816.0~1608.0 MHz . If anyone know what happen ,please suggest.

Check this picture (they claim):

Check this picture (show on hardware) :