The whole section confused me.

First, you can use the ins/2 function to assert that variables are in a range. We’ll use it like this:

There was no introduction to the syntax ins/2 meaning that predicate ins (why is it a function all of a sudden?) takes two arguments.

​create ​((A, B)) :- [A, B] ​ins ​ 1…7.

Shouldn’t that be 0…7?

Next, you’ll also need to check identity with #= (not ==)

Shouldn’t #= be =:=?