I asked moderator sir regarding this issue in this past (By asking that - if 12:35 is the charting time, then what should be updated - 12:30 or 12:45). He said there are no clear guidelines for this. We may update as per our own judgemnet
IMO, it is better to update as 12:30 (as it closer). Also in train availability page, that < symbol is not used. In PNR posts, that symbol can be removed (to avoid confusion).