That sounds about right from the Patrick Sawyer scenario.
IIRC there were roughly 200 contacts they were initially monitoring and of those between 5 and 10% later developed symptoms.
I saw something in the last day claiming Nigeria had 19 cases. I don’t know whether Sawyer is counted in that total. They only had a 40% mortality rate. They were considered lucky in that Sawyer presented dramatically, so was taken quickly to a hospital. It was rapidly recognized as Ebola and that hospital was promptly quarantined. So although there were a string of exposed victims initially, there wasn’t a chance for him to spread it to large groups when he was less sick. Not like the “Ø chance of happening” US case where he communed with the extended family and the ER before being recognized.