The article is confusingly worded, mentioning 25 passengers and 7 crew in another part... Which are also described as 25% of occupants, but that's not 25% of 198.
"a maximum indicated air speed of 358kt (662km/h), or Mach 0.9", while at 30000ft, Mach 0.9 is typically 983.7 km/h(source among others: https://www.globalaircraft.org/converter.htm)
Maybe "indicated" makes a difference, but so wide?
However indicated airspeed is still very useful as it measures the air resistance the aircraft is encountering which determines lift and airframe stresses (which is why the airframe speed limit is in indicated airspeed and not actual airspeed).
They were truly at 0.9 mach, had they increased speed by 11% they would have broken the sound barrier, well before the indicated air speed would have read a >mach 1 number.
"“Up to 24% of the aircraft occupants were rendered temporarily unfit for duties following the incident,” the report adds, referring to 25 passengers and seven crew members."
I read that as 'up to 24% of the 25 passengers and seven crew members'. I completely missed the quote at the bottom (beneath the image) that refers to the 198 people. And you're right, the figures don't add up anyway.