James,
The frame count is the same, up until I stop the Zfilm, at which time the Nix film ends. Hmm!!!
The perspective does not explain the speed in which Jackie slides back into the rear seat from (z411-z417) or 6/18.3 = .327seconds.
Use a stopwatch and let .327seconds expire.
.327seconds is faster than you can say "click click" or the mimicking of starting and stopping the stopwatch.