Does Calibrating the Dexcom at Both the Optimum Low and High Ranges Increase Accuracy

Thanks, everyone, for correcting my misunderstanding of how cgms works. I was told that the Dexcom cgms reads BS most accurately in the 60 to 160 range and that the Dexcom would be more accurate if you calibrated when stable between those ranges. Question: Will calibrating the Dexcom when her blood sugar is 70, and then again when it is closer to 160, increase the accuracy of the Dexcom, particularly regarding lows? Is it useful to have both a low and a high calibration point? For instance, if you calibrate at 70, the Dexcom still should not read 30 points above the low unless you are dropping quickly?