What Rivlas is talking about is the Independent vs Dependent rate. As you have had a child, you are automatically classed as Independent.
The Student Income Bank is basically, if you earn over the income cut off (which at the moment is $236 p/f) your credits will be used before your Austudy payments are affected by your income (providing you have sufficient income bank credits accrued). You accrue income bank credits each fortnight, and they decrease when you earn over the income limit.

Austudy is income and asset tested. So you will need to take into account yours (and partners) assets, income, and how much money you have in your bank accounts.