Why do you think it was just on a whim?, plenty of time between one estimate and another to think about it and change her mind for whatever reason. IMO her big mistake here was originally setting expectactions for 20 chapters. It's crazy to me to unnecessarily set yourself up for such a long-term commitment, specially when her storytelling doesn't seem to rely on a detailed and fixed roadmap. Just keep it vague.
As to the why cut it down your original estimate from 20 to 16 and now get it back to maybe 16-20 or even more, plenty of possibilities. Obviously only she can really answer, but I can guess:
- Chapter 11 took less time to develop than some of the previous ones, maybe she's more optimistic on being able to release chapters faster from now on. Some change on her way of doing things or she found some tool to expedite things, I don't know. The result would be she being able to release more content during the timeframe she had in her head for commiting to ORS.
- She got new ideas that make her more confident in being able to release something closer in lenght to her original vision than to what she thought when she cut down the estimated number of chapters.
- She plans to release shorter chapters so the content will be less spaced out between releases, so it would be the same content as with more chapters.
- For some reason (financial, a change on her personal life, whatever) she now thinks she would be able to keep her commitment to ORS for a longer time than when she reduced the original estimation.
I'm probably missing plenty of other possible reasons, or maybe it's a mix between more than one. Just keep in mind than doing a game like ORS takes writing, making art and coding, three of the harder human activities to accurately make estimations on. We have seen it in plenty of AAA games and those are projects with millions of dollars budgets and people strictly dedicated to estimate deadlines and make sure to meet them. Some of those games ended up in development hell and were canceled and some of them ended up being masterpieces.
To sum up, I'm not saying that going back to a possible higher number of estimated chapters is necessarily a good thing. As I said some other time we discuss this topic a number of chapters doesn't mean anything by itself, the quality of the content delivered on them does. But personally, I'm reasonably more optimistic with the most recent estimate as it could open up more possibilities for the less popular (among her patrons) paths to be fully realized. Or not, only time will tell, of course.