Old wives tale.  One just can't use figures like that.  Are you talking about
a population of 20,000 bees, or 50,000?  Are there 4 frames of brood or 12
frames of brood.  Is the nectar flow minor or major?

If the normal nectar flow in your area begins about April 15th, supers should
be in place BEFORE that date.  The "old timers" used to put one super in
place, add a second super when the first was near full, and likewise for the
3rd super, etc.; and lost swarm after swarm.  Scientific research during the
past 20 years has clearly shown the best supering is to put many supers on
ALL AT THE SAME TIME (read page
618 in the 1992 Edition of the Hive and Honey Bee).

Bees do not make any honey with supers sitting in your garage or basement.
Put the supers on a colony BEFORE the start of a nectar flow!

I hope I have helped.

George Imirie
Certified EAS Master Beekeeper
Beginning my 70th year of beekeeping in Maryland