The question should really be “why have the NodeMCU/Wemos people chosen to number the pins this way?”
If you were using an Arduino then D5 in the API would turn on digital pin 5 - so everything makes sense except what Wemos have done.
There a bit more on which pins are the best ones to use here, which is worth reading:
You should generate a new auth code in the app and use that instead of the one you’re using, because now that you’ve shared your current one on a public forum anyone can activate your relay whenever they like!.
Has that answered your questions, or is there more on the geofencing issue?
Once you have it set-up and working fully, I’d like to see a write-up and some feedback about how well IFTTT Location works, as this seems like quite a good solution to use for this type of scenario.
Pete.