2 cities, A and B are sending the same kind of units, u, to city C. A is 4 turns away. B is 3 turns away. u takes 1 turn to produce. A started sending first, and units from A were arriving before B started sending. C is producing a different kind of unit that takes 3 turns.
In city A, the display and hovering over each arrow shows:
> u > u > u > u > u
Production is sent to C; Arrives in C in 4 turns; Arrives in C in 3 turns; Arrives in C in 2 turns; Arrives in C in 1 turns
In city B:
> u > u > u > u
Production is sent to C; Arrives in C in 3 turns; Arrives in C in 2 turns; Arrives in C in 1 turns
So far, so good. But city C shows this:
< u u < u < u < u u < u u u
In production, then teleported here; Here in 3 turns; Here in 4 turns; Here in 2 turns; Here in 1 turn
(Also hovering over the first 2 units shows: Receiving production from B; Receiving production from A)
The number of units that arrived match what city C reports, as I recall, although I did not check closely.