Confused by haskell types [*]

I am beginning to learn haskell and am confused by the result of haskells type inference (see example below). Unfortunately I am not fluent enough in haskell to formulate the real question, so I have to work by example.

[*] As soon as I know the real question, I'll update the caption..

My goal

I am following the Get programming with haskell book. In lesson 10 a way to 'hold state' is shown:

-- The …