Hello Philip,
I suppose you are referring on the GSM Area Code, this information refers to Location Area code (LAC), it depends on GSM operator. It provides unique number which assigned to a set of base GSM stations.
For more information about the I/O Parameters Description, ID, and Data readings you may refer on this link:
https://wiki.teltonika-gps.com/view/FMC130_Teltonika_Data_Sending_Parameters_ID
Hope this helps.
Regards,
Patrick