Below is my attempt to re-do the calculations that led to that conclusion (this time, it's 4%).

FAI before WBE: 3%; Surviving to WBE: 60%; I assume cryonics revival feasible mostly only after WBE; Given WBE, cryonics revival (actually happening for significant portion of cryonauts) before catastrophe or FAI: 10%; FAI given WBE (but before cryonics revival): 2%; Heads preserved long enough (given no catastrophe): 50%; Heads (equivalently, living humans) mattering/useful to FAI: less than 50%.

In total, 6% for post-WBE revival potential and 4% for FAI revival potential, discounted by 50% preservation probability and 50% mattering-to-FAI probability, this gives 4%.

(By "humans useful to FAI", I don't mean that specific people should be discarded, but that the difference to utility of the future between a case where a given human is initially present, and where they are lost, is significantly less than moral value of current human life, so that it might be better to keep them than not, but not that much better, for fungibility reasons.)