[jwzimm]

I would expect that you should see a symbol where that arrow is pointing that corresponds to the three states listed on the valve body. Yours appears to be in an indeterminate state either past the allowed rotation or in between settings. If it is jammed I would leave it alone and contact a plumber who knows about those valves. Best not to mess with it and result in disabling the water supply to your house which would result in an emergency call to a pulmber.