The amount displayed is the available to bet balance i.e. current balance less current exposure, unless you have a green book on an express payout market where there may be a positive exposure.
The default balance that is shown when you first open Betting Assistant is your UK wallet.
If you navigate to an Australian market the software will automatically display your AUS wallet balance and exposure.
There is an option to display the balance from both wallets which you can set from Account in the Menu Bar where you can also choose not to display your account balance in the Info Bar.