Answer:
It was only 2 units up.
Step-by-step explanation:
A small increase in the volume would no alert the father of Sangram who is one room away, because that change would only be noticeable for Sangram who is in the same room, but when he doubled the volume from 15 to 30, it was more obvious for his father, one room away, that Sangram was using the remote control and that he was changing the volume in the TV.