Yeast Starter Calculations?

Looking at the Yeast Starter tab, I was trying to figure out how much of a starter I would need if I was propagating from a slant.  With no starter (slant only) the program shows a cell density of .1 billion cells.  Using a 1 quart starter, the program shows a cell density of .5 billion cells.  In BS2, there seems to be no way to increase the cell density beyond this point.  Even when using a 1000 quart starter, the cell density stops at .5 billion cells.
This is not limited to using slants either.  When using other yeast strains in liquid form, the cell densities do not change after a 1 quart starter.