I am working with a tutorial about "Setting up blueprints in Maya" on this site --->
The Blueprints - Reference Image Database - 20500+ blueprints online
I did everything the tutorial asked me to on setting up the blueprint images, but one part is not letting me change the settings of the images to fit eachother
Tutorial pic:

^ Thats the part i am at but the values that are highlighted on the tutorial "Need to change them to 30" are stuck at 10 and are non responsive in my program!
My Screen capture:
is there a setting that might be preventing me from changing the 10 to 30?
thanks