There might not be anything taxable. There are Ordering Rules:

https://www.investopedia.com/terms/o/orderingrules.asp

You need to compare how much they took from the various eligibility factors (various 5-year rules). It isn't clear if that rollover went to an existing Roth, and they had been making contributions there, outside of work. Or, the rollover was the new Roth, and that is the only source of funds, and took the distribution from the Rolled over funds, after it is considered Rolled.

So far, it seems nothing is taxable, but you know details we don't.