For Shravana Dwadasi vratam (Srisannidhi tradition), Which nakshatram and tithi must be excluded? Minimum how much nazhigai-s should the nakshtram and tithi association be?

The determination of Shravana Dwadasi vratam varies for Munitrayam and Ahobilam traditions. In the Munitrayam tradition, even if Shravanam is associated minimally with Dwadasi, Shravana Dwadasi vratam is on that same day – that is, if Shravanam is associated with Dwadasi either in the afternoon or the evening even for a brief period, Shravana Dwadasi vratam is on that day itself.
In the Srisannidhi tradition, only when both Shravanam and Dwadasi are present together till the evening, Shravana Dwadasi vratam is on that day. One can follow the announcement that will be made accordingly.