Adjusting Firecalc for 72t distributions

[whw55]

I am planning on early retirement starting in the next year or two.  Most of my funds are invested in a 401k.  I would like to use firecalc to simulate a withdrawal rate that is fixed for the first 10 years and then adjusted for inflation.

I ran the calculator using a fixed withdrawal (no CPI/PPI) with a life span of ten years.  I then used the average portfolio balance for a second projection for 30 years.

Is this an accurate calculation or am I missing something?  I would love to hear from others with the same issue.