what *precisely* means "--depth" WRT a shallow clone?

  i can see the standard use of "--depth" when set to precisely one,
for CI/CD systems that don't need any history. but what does it mean
to say, eg, "--depth 10"?

  the man page explains that as "a history truncated to the specified
number of commits", but what does mean in the sense of branching and
merging? will i get *precisely* 10 commits of history? and in the
context of merging, *which* 10 commits?

  sorry if this should be obvious.

rday