Oscilloscope displaying two voltage levels (on the same channel) for square wave
Why are there two lines? Does it represent a range?


No, it means you have persistence turned on on the scope. What is happening is the same signal is riding on another signal that is moving it up and down. The scope is showing many different triggers on the same frame. Turn persistence off or single trigger. Try using single triggering, and then keep single triggering. 

You may also want to look at your ground and how the signal is coupled to the oscilloscope. IE: DC vs AC coupling.