Planned time is the unconstrained profile ETA frozen the first time an aircraft matches the FCA — not a rate/MIT slot and not RDY. Actual is interpolated when the VATSIM track crosses the line. Enable Record crossings on an FCA in FCA Builder and leave it on.
Air froze while the aircraft was already flying, so the error is mostly the transit model. Ground froze before wheels-up, so it also carries however long the pilot actually sat there.