Simplifying this yields

PC < 47% * $2,330 * NIC
In other words, you can expect the EFC to increase with an additional
student in college when the original parent contribution normalized by
NIC is less than $1,095.

This is, of course, a simplification, since 47% is the maximum bracket
applied to adjusted available income (22% is the lowest). The constant
in the formula depends on which bracket was triggered. If it were the
lowest bracket, then the EFC will increase with an additional student
in college when the original NIC-normalized PC is less than $513.

In any event, this quirk in the formula only seems to apply when the
student is Pell-eligible (barring any significant income or assets of
the student).

Though it may seem counterintuitive at first glance, it does make
sense. When a child goes to college, the household expenses for that
child are significantly reduced, and are instead included in the cost
of education. When the parent contribution is low, the reduction in
family expenses per college student can exceed the change in parent
contribution.