Hi Jerry,
If Branch 03 setup was:
Branch 03
Localization: UK
Local Currency: GBP
System Currency: USD
the system would use the exchange rate (in the subsidiary) and store both the GBP and the USD amount of each journal entry; the GBP amounts would be stored in the Debit and Credit fields, the USD amounts would be stored in the SYSDeb and SYSCred fields. Your system is setup with GBP for both local currency and system currency though, so SYSDeb = Debit and SYSCred = Credit.
If you choose the "System Currency" option, the consolidation system is going to pull the SYSDeb amount from Branch03, and store it as Debit in the consolidation company, likewise SYSCred will be stored in Credit. The system is assuming that the system currency is the same currency as the local currency in the consolidation company, so it will not perform an exchange rate calculation.
Mike