[Exim] log statement clarification

Just for clarification as I cannot find this in the manual...
for some message that have delivery failures there is an 'error ignored'
log
line shortly followed by a 'Completed' log line, as near as I can tell this
is because I have exim configured to ignore return messages that have
delivery failures etc, and thus are 'Completed' (ignored/deleted/so-on).
This seems as it should, I am just looking for some clarification on when
the 'error ignored' lines are logged by exim.
Perhaps the manual/FAQ could be updated for this information as well.
If this is explained in the manual could someone please point me to the
proper section (however I cannot find the phrase 'error ignored' any where
in the manual or the FAQ).
Thanks!
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