special averaging method for inherited distribution for employee savings plan

My father participated in an employee saving plan.  When he died at 73 in (2005), my mother was the beneficiary of his savings plan.  She received distributions from his plan until her death last year (2023).  Myself and my three siblings then received a lump sum distribution of the remaining funds in the account.   We each received a 1099-R with the taxable amount and the state & federal tax withheld.  Turbo Tax is allowing me to use the Special Averaging Method for the distribution which reduces my overall tax liability by quite a bit.  Is it legit to use this method?   How does this work?  Is this something that I (Turbo Tax) will be carrying over for the next 9 years?  Needless to say, this makes me nervous...