Unexpected y_range

I start with this expecting that my outputs will be between -1 and 1.

learn = Learner(dls, cnn,  loss_func=MSELossFlat() ,y_range=(-1.,1.)  ,

and get this…

How are the predicted outputs not in the expected range?

Just for clarification, which chapter of the book is this , and which lesson is this from?
What is this graph about? Can you please share the code that plots this?

Whoops. Just realized that y_range is not a parameter of the Learner class. My bad.