By default, the video player rates (speeds) that your member can choose, is:

0.5, 0.75, 1, 1.25, 1.5, 1.75, 2

If you wish to add more speeds, add it here, separated by commas.

E.g., if you wish to add the speeds of 0.9x and 1.4x speeds to the video player, here's what the new list would look like:

0.5, 0.75, 0.9, 1, 1.25, 1.4, 1.5, 1.75, 2

Enter the new list into the Video Player Rates field in Settings and click "Save Changes".