Interface Tick

Cumulative day volume (Quote mode).

Last-traded quantity (LTP mode).

Open interest as at this tick, where the feed carries it. Unlike the two quantities above it is not accumulated into the bar: it replaces, because it is a level and not a flow (see Bar.oi). A feed that does not report it leaves the built bar without one, which is the honest result rather than a zero that reads as "nobody is holding this".