Tvheadend

I'm using Tvheadend 4.1-1692~gac48dc2 and I would like to try the DVR Autorec Duplicate handling feature to record only new episodes of a series, ignoring reruns. I tried many combinations, but every time all the episodes are added to the Upcoming recordings (with different combinations of values in the column "Rerun of").
For example if I select "All: Record if different subtitle" I would expect to obtain only one recording for each episode (the episode number is in the subtitle). All episodes are added, and the column "Rerun of" has values on duplicate episodes.
But my question is, will the duplicate episodes be recorded anyway, as they appear on the list of upcoming recordings, or they appear only as a reference and will in fact be ignored (if the original episode was already recorded correctly at the time of the rerun)?