Your brother is sitting there as "punishment" for his failure to appear (or, more accurately, to ensure his appearance at the next hearing). It is unlikely that he would get jail time for a misd. traffic ticket unless he has a serious offense like DUI or a very long record. However, unless the Judge specifically does not give him credit for the weeks in jail, he would automatically get credit for that time either against any jail time or against any time he has to serve on probation. As a general rule, I have found that persons held on a bench warrant do get credit for that time in Georgia.
If there are fines and your brother cannot afford to pay them immediately, he is likely to be put on probation at least until the fines are paid.
If you planned to put the cash bond up yourself, you would get it back from the city/county once your brother's case is over. However, if you hire a bondsman, the money you pay to the bondsman is his/her fee for putting up the cash and you will not get that money back.
If your brother has a lawyer, the lawyer can consult with the prosecutor and find out if he/she has a recommended sentence for your brother if he were to plead guilty to the offense. That would give you some idea what he can expect on the 27th.
The biggest ommission from your question is the nature of these traffic tickets. Is it a DUI case? If so, you can expect 12 months of probation for a conviction, minus the days spent in jail. All jail service time will count. Depending on the circumstances leading up to his failure to appear, and depending on his prior criminal history, the court may release him on the 27th. Best of luck to your brother.