Best match offset
Best match, a part of algorithm transparency, is a simple record produced at the end of matching that points to pairing with the highest score.
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Best match is stored as a UTF8-encoded decimal number. It is the offset of the pairing with the highest score. Pairings are counted in the same order in which they appear in transparency data and in root list, starting with offset 0. Best match may be -1 if there were zero pairings to choose from.