I’ve found that new sensors can take time to settle down and the time it takes can be different from sensor to sensor. One sensor I had took 24hrs to settle and it ended up being one of the most accurate sensors I had for the remaining sensor life.
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Dexcom is known for giving false lows the first day for some people (I don’t know about highs).
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Suppliers are mandated to follow certain guidelines. If they said your Dexcom had to be “off” by 46 points I’m guessing they were comparing your reported fingerstick to your CGM reading and going off this chart, which shows what the 20% difference works out to numerically.
https://cdn.media.amplience.net/i/dexcom/en-us-g6-meter-g6-comparison-table?qlt=default&fmt=auto
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A federal regulation says Dexcom has to publish specific accuracy information in the user guide.
Page 285 Table 1-A. G6 Accuracy to YSI (Lab glucose meter) (n=325)
Adults Day 1 Percent within 20/20% YSI is 87.1
Dexcom G6s take readings every 5 minutes so that is 288 readings on day one. Only 251 of those have to be within the 20% range.
I like Table 1B on the next page. With a little math it tells me over a 10 day span of 2880 readings when the G6 is displaying a value between 70-180mg/dL twenty readings can be off by more than 40%.
My Contour Next blood glucose meter manual says it will be within 15% 99.7% of the time. BGMs aren’t always accurate.
You did the right thing double checking the Dexcom when you didn’t trust the number. It was in the ball park. Would it help for us to share things we do to get consistent numbers out of our G6s?
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This is great info. Thank you
And it has settled took 24 hours just like they said.
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Great to hear! Hope it works out well for you
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If you use Control IQ and have issues with the sensor readings the first 24 hours, you can turn off CIQ and use your fingerstick reading when dosing for meals. But don’t over-calibrate - as stated in another thread, that can cause issues of its own.
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And yes I overcalibrated Sigh. Ok I didn’t know this. Thank you 
You’re welcome. Hopefully that helps some. We never stop learning!