See my reply to BrowserUk, who asked a similar question.

Basically, the whole idea is to save space; the more the better (by definition). The numbers, even though "normal" sized, are like BigInts variable-sized in their encoded form, and 0 and other small values have the minimum 1-byte length.

Since I already know the total size, I can remove one value from the delta list and still figure it out again.

So the answer to why is "because I can". The requirement is for minimum space and demonstratable (not optimal) logic to deal with it.

Thanks,
—John