"She's fine, doing well," Mr Wiratna said on Thursday.
"I will announce (the release date) after I've seen the clemency letter," he added.
A senior prison official has already calculated the release date which, based on the almost two years in remissions she has already received on top of the five-year cut, shows she has another five years to serve.
The sentence could be reduced further, and possibly end in 2015, if the 34-year-old is granted the maximum eight months in remissions over the next two to three years.
However, it has been revealed that Corby may taste freedom even sooner if she is approved for an Indonesian prison program of "asimilasi", or assimilation, designed to allow well-behaved inmates to reintegrate with society.
Under the rules of the program, prisoners must have had their final legal status determined. Those convicted of drug offences must have served two-thirds of their final sentence.
If Corby receives the maximum remission of six months in August, she will qualify for the program this year.
She would have continue to demonstrate good behaviour to qualify for "asimilasi".
Mr Wiratna confirmed that Corby would be eligible for the program.
"I think every convict, local or foreigners, have the rights to have it," he said.
"Her behaviour has been good."
Corby's lawyer, Iskander Nawing, said he was likely to apply for his client to take part in the scheme.
"Probably we would go there, for assimilation and parole," he told AAP on Thursday.
"Certainly behaviour will be considered if she is to be allowed to do it, but I think there is no problem with that."
He said the fact Corby had already been given almost two years in remissions in the past showed she was a well-behaved prisoner.
Prisoners taking part in the program are allowed out during the day to work, but must return to the jail each afternoon.
The head of security for Kerobokan jail, Wayan Agus Miarda, confirmed Corby could qualify for the program.
"About the program, there's a team to assess her, which consists of our officers," he told AAP.
Mr Agus said that from his assessment, Corby had been a model prisoner.
"I see her following the regulations in here, I don't see her doing anything bad.
"She mingles with other inmates and communicates with the prison officers.
"There's no bad report on Corby so far."
The development comes as doubts continue as to whether she would be granted parole, which she would also be eligible to apply for after having served two-thirds of her sentence.
But parole is very rarely granted to foreigners.
A spokesman for the prison director-general in Jakarta confirmed on Thursday that if parole was granted, it would have to be served in Indonesia.
"If they break the law, then their parole will be revoked and they will have to serve the remaining sentence in prison," he said.
The former beautician from the Gold Coast was busted in 2004 while attempting to smuggle 4.1kg of marijuana into Bali in a bodyboard bag.
Corby was granted clemency last week when Dr Yudhoyono cut five years from her sentence.
-AAP
