If the found time zone is equal to company time zone (e.g. CET) in transaction /PACG/ECM_COMP - Company definition and the time zone id in this transaction is maintained (e.g. “Europe/Berlin”), then the time zone id would be taken from the company settings and not from time zone conversion customizing table (/PACG/ECM_TZCNV).
If the setting above is not maintained, time zone id can be set in transaction /PACG/ECM_TZCNV - Time zone conversion. The first field contains a formal time zone while the second one is an up to 50 characters description. E.g. 'Europe/Berlin" can be converted to "CET".
The following table can serve as time zone mapping help resource: https://en.wikipedia.org/wiki/List_of_tz_database_time_zones