Hi! Thanks for adding the unit numbers. building:units is (perhaps confusingly) for the *number* of units; addr:flats is for the (semicolon-separated) list of units. So a better way to tag that building would be building:units=2 and addr:flats=A;B. 

Thanks again and welcome!
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            Published using OSMCha: https://osmcha.org/changesets/138874732
            