It got so big becasue the service highways that you added did not connect to pre-existing and unmodified nodes belonging to Pipariya Road thereby modifying it. Changeset bounding boxes envelope the entire area occupied by an element so the size is now based on the length of that segment of Pipariya Road. Consider how you structure you contributions to OSM. Bear this in mind for your future contributions and thank you for what you've contributed thus far.