The 9550 value is an approximation.
Looking at the BH curves in the material datasheet, you will need to determine the slope of the curve around H=0. Since neither temperature curve actually goes through the origin with these being the hysteresis curves, you are basically needing to eyeball the midpoint and do your own rise-over-run determination.
As an example, if you draw a straight line from B=0 to B=100mT, this would bring us close to H=8A/m. Then, to determine mu_r,unsat, you need to divide this slope by mu_0:
(0.1 T / 8 A/m) / (4pi10^-7) = 9947, which was then rounded up to 9550.