Double Teleportation while falling down

I expected to get teleported once into the air while falling down

The important thing about the falling is, that I'm not on the ground/ flying at the point i execute the command

I got teleported twice to (i think) the same Point (while falling down)

/tp @p//PlayerName ~//[or Absolute Coordinate] ~10 ~//or Absolute Coordinate

(You can't see anything unordinary on the picture)