balance between snapshots

[Golddouble]

I am a bit confused:
After an "incremental" snapshot, Vorta says, that the size of this "incremental" snapshot is 140.5MB.

As next step, I have compared these two snapshots with the difference tool of Vorta.
I would expect, that when I add all "+" balance, then it should be about 140 MB or even more, because I guess, that the values showed in the difference window are not compressed.

So I have added all the + differences (balances). But I received a sum of 70 MB at most.

How can this be? What do I miss?

Would appreciate some answer. Thank you.

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Sorted according to balance: