I was told "You had ABP interest adjustment (Schedule B)." Where is this found ?

https://ttlc.intuit.com/replies/5200852

This does not answer the question.  Where is the calculation for this value found?

A premium is an amount paid above par for a bond. The amortization of the premium will depend on the term of the bond and the method used, such as straight-line or the effective interest method. You would need the information from the bond indenture to determine the amortization amount. For tax purposes, it will be reported on the 1099-INT. 

TurboTax program should explain the specific calculations used each value in my return, and it should link back to the sources of the values used in the calculation.   I shouldn't have to do an internet research project and guess how the calculations are done.  This is one such case, but there are many others.  Please work on improving the transparency of the calculations.  That will save users a lot of time checking.