Stable figure took 30 minus to finish, and ambiguous figure took 60 minus to finish, overall it took an hour and half to finish.
In this phase, the project compare to previous one. I used more time to finishing it, and I also changed some small detail. However, you can still easily figure out which one is stable and which one is ambiguous. One thing, this phase is better than the previous one is that the dark space is more completely and filled than the previous phase.