The attached document details the Book Value logic used on the Book Value report in the Dashboard Reports General Ledger folder. 

The document defines the Book Value logic for a Capital (Direct Finance) Lease, Operating Lease, and Loans. 

As noted in the attached document, choosing different parameter values will affect the "Book Value" that the report calculates.

The Book Value report has the ability to exclude by Contract Item type, so if all item types aren't chosen, this could result in a difference from the Accounting screen.

The Book Value report also has an "As of Date" parameter.  In order to match the values on the Aspire Accounting Screen, use the current date to run the report.