Snapshot size does not correspond to # of blocks and block size?

Summary:

I changed a dimension from dense to sparse in Test, but the snapshot size has not changed as much as it should have, judging from the resulting # of blocks and block size. What am I doing wrong and / or how to calculate the snapshot size?

Content (required):

I have a BSO Planning application with 9 sparse and the following 4 dense dimensions:

D1 - 220 members stored (accounts)

D2 - 13 members stored (time)

D3 - 4 members stored

D4 - 1 member stored

Due to a change in business requirements, the contents of D3 have changed and the data has become sparser (and will become even more so) which is why I'm preparing to changing it from dense to sparse.