weird "optimisation levels" in man page

Man page shows this:

   Optimisation levels
       -O0 -O  -O or -O1 -O0  -O2 -O0  -Odph

This looks very weird:

• Why -O and -O0 listed twice?
• That or looks weird, how do I read that?

Apparently the man page is auto-generated from the user manual(thanks @int-e), and while doing that "reverse" column is also included. We should probably either ignore "reverse" column while parsing the user manual parts or somehow re-format generated man page lines.

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Trac field	Value
Version	7.10.2
Type	Task
TypeOfFailure	OtherFailure
Priority	lowest
Resolution	Unresolved
Component	Documentation
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