When you add a timer for a frame, it’s called a transition timer. Suppose your frame N is stopped at color A and you add a frame N+1 with a duration X and color B, then the logic is: change the color gradually from A to B in time X, the total step the transition costs = (X / 20ms), here 20ms is the transition granularity.
We dived the changes to very small step in order to make all the color changing smooth enough.