Actual physically new sensor is always using the code from the sticky label on the underside of the sensor.
You are still on G4 - right? When you see the G6, it makes more sense.
Here is an image I lifted from diatribe (thanks diatribe!!!)
This is a new G6 insertion device (upside down) which has the sensor inside of it. As you can see, the code (5937) for the sensor is on the bottom of the device. Once you have used a number of G6 sensors the codes start to look familiar. We have probably seen less than 10 different unique sensor codes. I don’t understand what they do or why one sensor has a different code than another. But my only reasonable assumption is that it is important and makes a difference.
So, on a new physical sensor, I will use the code from the label on the actual sensor.
I then keep the sticker with the code as well as record it in a spreadsheet such that if I want to restart later then I have the proper code.