This calculator is based on the pay matrix for CFTIs described in this order. The algorithm is general, and may be adapted for other pay matrices by suitably editing the part of the accompanying code which calculates entry pay and fitment factor for a given grade pay.
The debunching calculations are based on the clarifications in this office memorandum (specifically, paragraph 8), as explained in these slides.
This calculator does not address anomalies that may arise after the initial fitment.