Tracy-Gregory Gilmore, I believe you are correct. I think Charles just forgot the “returns” word near the end of that sentence. It should read as you have it: “takes1Param requires 1 parameter––a function that takes an Int and returns another Int”.
In the next paragraph he seems to confirm this signature notation.
map : (a -> b) -> List a -> List b
map f list =
Here parentheses are required because f is of type (a -> b), i.e. a function that takes a single parameter of type a and returns something of type b.