Priority. The order machines serving one room take it in: the lead is offered the whole load and the latent, the next what the lead did not deliver. Several machines on one room.
When two machines serve the same room they could split its load in shares, and a share is always wrong for one of them: the load being divided is sensible only, and the machine doing the latent work — a DOAS — must not be throttled to a fraction. So machines take a room in turn instead. The leading machine is offered the whole demand; the next is offered what the lead did not actually deliver; equals divide what reaches them.
Declared rather than inferred, because nothing in a graph says which machine is the outside-air unit. The rule has a moisture side too: the machine behind a lead is asked for the supply humidity that lands the room on its bound beside the air the lead delivered, so a DOAS carries the latent and the handler behind it only the remainder. One wart to know: a lead's own unmet count reads hours it could not cover alone — the room's count is the comfort truth.
Open the builder — the examples in the Design tab's sources list include a machine of this kind, and the Simulate tab runs it against a year of weather.
DOAS — dedicated outside-air system · SZVAV — single-zone variable air volume · VAV terminal box · Economiser · Waterside economiser · Demand-controlled ventilation · Face-and-bypass · Head-pressure control · Humidity ceiling and floor · Cycling and modulation · Coupling · Category · Nested system · Design point and TMY year