Google Maps Api – when is map.panto(latlng) smooth

Can someone please explain in pseudocode, or at least less ambiguous language, the API Refence Manual definition for smooth transition requirements of the panTo() method: –

panTo panTo(latLng)
Parameters: latLng: LatLng|LatLngLiteral The
new center latitude/longitude of the map.
Return Value: None
Changes the center of the map to the given LatLng. If the change is less
than both the width and height of the map, the transition will be smoothly
animated.

Specifically, what is “the change” in this context?

Example: –

Zoom Level = 6
LatLng1 = lat: -31.9523, lng: 115.8613 Pixel X = 13464 Pixel Y = 9728
LatLng2 = lat: -33.8688, lng: 151.2093 Pixel X = 15073 Pixel Y = 9831
Current Map Center is LatLng1 and panning to LatLng2
I make the "change" to be horizontal 1609px and vertical 103px

If the map’s DIV container is at least 616px wide and 344px high the pan is smooth if not it jumps.

Can someone please help me heuristicly marry up those figures with an algoithm?