Calculation of Jail Time Credit can be very frustrating. Your jail time credit should have been calculated before you were sentenced and then addressed at sentencing. It is very difficult to get JTC addressed properly post-conviction when it was not addressed at sentencing.
The case law in Ohio is all over the place when it comes to jail time credit issues. Most such problems are addressed on a case-by-case basis, as the facts and surrounding circumstances of addressing jtc at sentencing usually have bearing on the outcome of trying to convince the court to correct the sentencing entry.
If the Ohio Public Defender cannot assist you in trying to correct the jtc, then you should attempt to contact your attorney of record who handled the case, plea (or trial) and the sentencing. They could file a motion with the court asking that the jtc matter be corrected. Good luck.