In brief
animation-duration sets the length of one cycle rather than the total time for every repetition. Two iterations lasting 1s give two successive one-second cycles, excluding delay.
Useful to know
animation-duration sets the length of one cycle rather than the total time for every repetition. Two iterations lasting 1s give two successive one-second cycles, excluding delay. [1]
This distinction helps synchronise effects. Also inspect iteration count; duration alone may not explain the complete observed time.
Sources
For further detail and to check the information: