I think what's happening here is that both --depth options get applied,
one after the other. The following command behaves exactly the same:
ledger bal --depth 4 --depth 1
The reason for this is closely tied to the way these "filters" are
applied in ledger, so I think it isn't that easy to change this without
However maybe open a bug on GH to discuss whether this should be changed
in the future? I do see the appeal of having later --depth options
overwrite any earlier ones, it does feel more sensible to me as well...