What is the Roth Conversion Optimizer objective function? What is it optimizing?

Fairly new but really liking the product and details. Two questions about the topic:

1. Optimize always asks how many years to convert. I say 4. I have 4 years before RMDs. It always ignores any number I enter. What am I missing?

2. The Optimizer minimizes conversions for 3 years, spikes once, then hits a steady state until we die. I assumed we'd be aggressive for 4 years. We have plenty of regular savings to pay the taxes. And this aggressive approach maximizes networth and gives us the insurance we seek against the tax time bomb and likely spikes in IRMAA and income tax. So I can't figure out what Pralana is thinking.

Help will be much appreciated.

-- Brian