I think I was wrong in an earlier post when I said the vial should be bigger than 25mL in order to get closer to the 4.5B/mL number. They tell you the cell count and a bigger vial would just mean the same cell count in even more volume (5mL vs 2.5mL in my example above).

Well, those really look like 50 ml tubes to me. By your method, that would give slurry concentrations of:

50.0 M/ml, 50.4 M/ml, 49.7 M/ml, 50.0 M/ml, 50.9 M/ml

But maybe that is not what the picture is actually showing. Is it possible that each tube was filled with 50 mls of slurry at the concetrations listed, and then allowed to settle? And the amount of settled yeast is then listed as a % of the volume?

If you put 50 mls of 2.5E8 cells/ml in a tube and let it settle, you've got 12.5 B cells in the tube taking up 10% of the space, and the settled yeast is at 2.5 B cells/ml. .

50 mls of 6.3E8 cells/ml settles out to 25% of the space and holds 31.5 B cells in 12.5 mls for 2.52 B cells/ml.

Running the rest of the numbers the same way gives you ~2.5 B cells/ml for all of those slurries. This seems more likely to me.