50? Just initially, but in a week or two more of these developed symptoms, so more recent number was just 18%:

https://www.cebm.net/covid-19/covid-19-what-proportion-are-a...

"Setting: Diamond Princess cruise ship, Yokohama, Japan (n=-634 tested positive).

Proportion: 18%"

Also:

"23 Residents of a Long-Term Care Nursing Facility King County, Washington

10 (43%) had symptoms, and 13 (57%) were asymptomatic."

But then:

"Seven days after testing, 10 of 13 asymptomatics developed symptoms"

That means that just 3 of 23 remained asymptomatic there too, i.e. 13%.

It is estimated that the people mostly spread this virus exactly in the phase where they still haven't developed symptoms, and the virus can be detected. But that doesn't mean they will remain without the symptoms.