This response only explains that the ABP Adjustment comes from a 1099-INT. It does not explain where to find the calculation of the value. The program does not have a link to the data source, nor any help from the Data Source button. Aargh!
The reference link in this post is nice, but the program should have this explanation in the right-click "about interest adjustment", and it should have a "Data Source" link back to the calculation or source value.