Wow, this is an old thread…
There has been a lot of discussion on how the AMS calculates remaining filament, and as it turns out it does not use the GUID of the RFID tag to track it.
Bambu has since also given a 10,000 foot explaination in a wiki article on the main AMS functions.
The RFID reading process can also be used to estimate the remaining filament. The working principle is to estimate the percentage of the remaining filament on the spool by the length of the filament sent out after the RFID tag on the spool rotates a full circle. The complete 1kg filament roll is 100% capacity by default.