Sugar Experience file & .bin book Which takes priority?

in other words, which does the engine use first - the exp file or the bin file? Thanks

Bin data replace evaluation. Experience data fix bad evaluation.

Thanks. That means if the Experience (.exp) file has a better line than the one in the book (.bin) file, the engine will select the better line from .exp instead of from the book.bin Correct?

Experience data is called by the evaluation. If the position exists into the bin data, there is no evaluation.

got it, many thanks!

So I tested engine1 with blunder.bin book and strong.exp file enabled Vs. engine2 with strong.bin book enabled and no .exp.
Result: engine1 always loses regardless how experienced the exp file is.

Question: at what point if any, does the experience file correct an engine's move if it's book contains a blunder?

Never ! It's not the goal of the experience file. The book replaces the evaluation. Without evaluation, no experience data is used.