Help from expert please- Barometric Damper

If anybody could help me I would greatly appreciate it. Oil-fired boiler with baseboard heat. 5 zones of water circulating, one circulator, multi zone setup. Since we bought the house there was a sheetmetal screw preventing the damper from moving. During our yearly cleaning, the screw was removed, and for the first time I actually realized what the damper was. Anybody that can help me with a ballpark as to how to set the weight please watch the video, it would be greatly appreciated