Ok here goes

Fee is $3300
I don't know what the actual medicare rebate on it is - lets say $500
So you are left with $2800 out of pocket.
This takes you over the medicare safety net (lets assume that you have claimed nothing all year) and you get nothing of the first $1100 out of pocket back, which leaves us with $1700
Once you have reached the safety net you get 80% of out of pockets back so you will get 80% of the $1700 back - which is $1360

So in this ficticious example, you will get $500 (the actual rebate) and $1360 (the safety net figure) back so a total of $1860 of the $3300 that you spent.

This is all assuming that you reach 20 weeks before 1 January next year when everything will most likely change (I've got tickers turned off so I can't see when you are due sorry)