This has been added to the documentation but should be fairly apparent once you select the option, allowing you to specify a transition time (the total amount of time it will take to get to the new states) and transition interval (the spacing between the repeated commands the app will send, each with some in-between values to eventually get you to the resulting state). This is similar to the "...over time" actions in Rule Machine.
These are explained if you click the link that goes into the discussion about replicating Groups and Scenes behavior, which takes you here:
