Without going into to much details, the Dexcom tries to adjust what it displays based on what it measures and on a linear fit calculated on the six last calibrations (that was the case before the Artifical Pancreas firmware update, not 100% sure of what it does now). That's why you may see the Dexcom trend higher, or trend lower than your BG at times. Since six calibration points are involved, one single calibration will not necessarily change the displayed value much, or in the expected direction. Here's a very schematic example of what that can lead to: a correction below the value could actually cause future measures to be too high in some circumstances ![|640x480](upload://yK59AcnM3cZUFfM82aoq73ucaTV.jpeg)
It's of course a bit more complicated than that in reality and, in practice, there is no need to worry about it as long as the Dexcom operates within its specifications.