That number isn't something the CDC have said. The CDC report lists a number of planning scenarios. > Are estimates intended to support public health prepared

That number isn't something the CDC have said. The CDC report lists a number of planning scenarios. > Are estimates intended to support public health preparedness and planning. > Are not predictions of the expected effects of COVID-19. > Do not reflect the impact of any behavioral changes, social distancing, or other interventions. The number you're quoting is derived from (but not quoted in) one of the scenarios, which is described: > Scenario 5 represents a current best estimate about viral transmission and disease severity in the United States, with the same caveat: that the parameter values will change as more data become available.