In a relative position encoding mechanism, a hyperparameter n_b is used to define the number of parameter buckets. A specific calculation, (n_b + 1) / 2 - 1, is used to determine a boundary for categorizing relative distances. Describe the relationship between n_b and the result of this calculation. Specifically, if n_b is increased, what happens to the calculated boundary value, and what does this imply about the range of distances being grouped together?