First, you have to make sure what you mean with the term "Count-in"
For example if a band wants to start at the 2nd Verse (i.e. bar 20) and the drummer gives a one bar "count-in", then he just counts 4 beats on his drum sticks and the band starts at the 2nd Verse at bar 20.
Enabling the "count-in" in Logic is just a preroll, that means that Logic starts the playback at bar 19, one bar ahead of the actual start of the Verse2 at bar 20.
This "count-in" aka "preroll" is only possible in conjunction with the Record Mode and not Playback Mode. If you want playback to start at bar 19, you have to put the Playhead there of set the Cycle Range to start at bar 19.
Hope that helps
Edgar Rothermich - LogicProGEM.com
(Author of the "Graphically Enhanced Manuals")
http://DingDingMusic.com/Manuals/
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