You cited Mark Winston stating that there were 15,000 cells (counting both
sides)
on a deep frame.  I believe that is wrong by a factor of 2.

It is a well established fact that, Italian, Carniolan, And Caucasian bees
build comb
that comprises 55.3 Cells per square inch counting BOTH sides of the comb.

Foundation that fits in deep frame measures 16.75" long x 8.5" high which
equals
142.375 square inches; and 142.375 time 55.3 equals 7,873 total cells.

George Imirie