Dexcom g6 + xdrip + monitor

Hi everyone, I just a dexcom g6 after using a g4 for a long time. I like the simplicity so far and the thiner profile if the sensor.

I have one issue which I am not sure if anyone else has dealt with. I have a phone that doesn't support the g6 app, so I use xdrip. But because I am not sure I connected my g6 to the monitor also.

Can I run the sensor straight from G6?

Xdrip shows different sugar level than monitor around 40 unit difference, why is that?

Any help will be appreciated.