Well that gives us a general timetable for when the stock market might conceivably see the light at the end of the tunnel, and start rebounding for good.
So if deaths peak in 3 weeks, by the fourth week the 'new case' statistics will start to drop, which will be the sign that we're on the mend, and up go the markets in anticipation (maybe).
But at least it's a 'data point'. 3 weeks would be great since the disruptions done to the economy should be readily reversible. On the other hand, if the virus would go on for 6 months, we've got serious problems.