The reason as far as I could decipher Milon, is that there is a Main Line Barddhaman Howrah EMU local departing at 12.25 pm and hence, 13116 has been scheduled to depart 10 mns after that, as both trains have common path upto Shaktigarh. That is probably why it gets held up at Barddhaman even if it arrives there by 12.15 pm.