The .8 is a moot point .The common procedure is to check 3 times and average the readings. I would round it off to 45 Rc. Sometimes one reading is taken to check that it's been hardened [sometimes the unhardened are mixed with the hardened !] Hardness spec should always be a range [i.e 57-59Rc ] rather than a specific hardness .Steel chemistry variations from batch to batch and even more from one maker to another will result in hardness variations....If a heat treater doesn't heat treat the part properly he has a responsibility to re do it or refund your money.
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