Minimum active should be filled in when creating a FeedBin.
Minimum active is the change from the last inactive state of the Feedbin (generally a fill) Point 1 in the image below and the current reading. If Point 2 was the current reading and the minimum active was set to 0.1 tons (Point 3) then the bin will be set to active as shown at Point 4.
To summarize, the minimum active is the minimum change in tons to change a Feedbin status from inactive to active.
Only one bin in a group of bins can be the active bin. The ADFI calculation is based upon the currently active bin.