Description of the command line option 'keepRelative' has some mistakes:
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--keepRelative, -R
                Alternative deletion scheme. If you use this option, all
                other keep options are ignored. Preserves backups depending
                on their relative age. Example:
                -R '1d 7d 61d 92b'
                will (try to) ensure that there is always
                - One backup between 1 day and 7 days old
                - One backup between 5 days and 2 months old
                - One backup between ~2 months and ~3 months old
                If there is no backup for a specified timespan
                (e.g. because the last backup was done more than 2 weeks
                ago) the next older backup will be used for this timespan.
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Correct should be '92d' and the second interval means between 7 days and 2 months.