Jordan Wayne Beroukas on Friday told the ACT Supreme Court the first time he got locked up was on his 18th birthday.

Now 24, the Braddon man said he was determined to change for the sake of his two-week-old daughter, whom he is yet to meet.

Beroukas was fronting court for a sentence hearing on an arson charge, having admitted he damaged an Alexander Maconochie Centre cell by fire while he was on remand for fraud offences.

A statement of agreed facts reveals the ACT was subject to a total fire ban at the time, in December 2019, as "extensive, uncontrolled bushfires" burned in surrounding parts of NSW.

CCTV footage played in court on Friday shows Beroukas enter a cell and place a sheet across the open doorway just before 5pm on the day in question. While he is still inside, a flame ignites.

"As the flame grew and began to engulf the sheet, [Beroukas] left Cell 7 and took a seat on a chair nearby," the facts say.

Another inmate can eventually be seen on the video racing up a set of stairs and throwing a bucket of water on the fire.

The total cost of repairs needed as a result of the blaze has since been estimated at about $2300.

When Beroukas took the witness stand on Friday morning, he told the court he had been "immature" and "didn't realise how stupid it was at the time".

He conceded he was "lucky no one got hurt" and admitted he was "probably trying to impress people [he] shouldn't have been".

"This charge is from 2019 and I've grown up a lot since then," Beroukas said.

"There was a lot of peer pressure involved and shit."

He said the CCTV showed he had raced back to the cell once he realised how big the fire had become, adding: "You can't mistake my mullet."

The court heard Beroukas had recently been granted parole for other offences, but he was still behind bars.

He said he would attend a drug rehabilitation program when he was ultimately released in an attempt to avoid reoffending and being returned to custody.

Beroukas told Associate Justice Verity McWilliam he was "100 per cent" committed to changing his ways and becoming a good father.

"I was a bit of a shithead of a kid, but I've apologised to my family and that," he said. "We're all good now."

When Beroukas told the judge he had been in and out of jail since his 18th birthday, she exclaimed: "Oh, Mr Beroukas!"

"If ever there was a time to change your spots, it's now," she said. "You're throwing your life away in jail."

Associate Justice McWilliam went on to describe the birth of Beroukas' child as life-changing, joking: "It's a prison sentence in itself in some ways."

The 24-year-old's lawyer, Sarah Avery, urged the court to consider deferring Beroukas' sentencing for a few months to allow the young man to prove he was capable of changing on parole in the community.

Ms Avery acknowledged this was "a big ask".

Associate Justice McWilliam told Beroukas she would decide on Monday whether to immediately sentence him for the arson or defer sentencing.

The judge had earlier agreed with prosecutor Marina Lucero that another sentence of imprisonment was ultimately "inevitable".

She indicated she may, however, consider allowing Beroukas to serve it in the community.

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