Milwaukee refractometer info needed

[leadsinker]

got a milwaukee refractometer. my question is, when looking through eye piece i have issue with reading properly. yes i have turn fine tune fcous. some times i see a darker shade of blue on top with lighter shade of blue below. other times i see dark blue on top then a white or clear line in between the light shade below. what is the proper way of viewing this,dark shade top,light shade bottom or dark shade, white line in between light shade on the bottom. is it just a matter of lighting and position to obtain proper view.

thanks