C.29.BB:4.4 - Redraw the boundary by reclassifying the same exchanges

When enlarging S, include the added stores and their changes. Transfers between the old and added parts become internal only if both sides now refer to the same amount over the interval. The new exterior crossings remain.

When shrinking S, formerly internal transfers can become inputs or outputs. Recompute the requested total from the retained stores. A balance for a larger region supplies its total; obtaining a smaller region’s value still needs the removed region’s amount or a sufficient bound.

Check the two descriptions against each other: the larger total equals the sum of its disjoint parts, and their changes agree after shared transfers cancel. This comparison can expose an omitted connecting store without resolving every internal rate.

Changing the parts over time can also change membership. Include that effect through boundary crossings or a suitable population rule; keep it visible when comparing successive totals.