"Worksheet Exercise 1.11.1.3"
Suggests you are inside a "worksheet" division. (That was not included in your
snippet.)
"exercises" in another "specialized" division. They do not nest. The schema
will tell you that. Specialized divisions are always terminal.
Said differently, an "exercise" can go in a "worksheet" or in an "exercises" but
not both. (And it can go other places.)