Toowoomba's Wagner brothers were defamed by a 60 Minutes report from May 2015 that incorrectly insinuated they were responsible for the destruction of the town and deaths of 12 people.

They argued the report insinuated the collapse of a wall at a Lockyer Valley quarry they owned caused the "man-made catastrophe".

The report, entitled 'The Missing Hour', described the wall of water that fatally swept through Grantham as an "inland tsunami".

The report did not expressly blame the four Wagner brothers for the deaths but the family believes it led people to believe they caused the disaster, sought to cover it up and refused to answer to the public.

Nine's lawyer, Sandy Dawson SC, on Monday said Justice Peter Applegarth erred when he calculated the payout to the brothers and his client should pay a much lower figure.

He said the judge had treated the 60 Minutes broadcast and journalist Nicholas Cater's words as two different publications of the same defamatory material.

"That resulted in double compensation, for the respondents were compensated for Mr Cater's words twice," he told the Brisbane Appeal Court on Monday.

Mr Dawson said it was also incorrect for Justice Applegarth to treat Nine's failure to apologise to the Wagner family after it was learned their report was wrong as an aggravating feature.

He said his client was still fighting a court case at the time based on the truth defence that the broadcast did not defame the Wagner family.

"That defence was a reasonable one and reasonable one to hold onto," he said.

Mr Dawson suggested a payout of $475,000 each for Denis, John, Neill and Joe Wagner plus interest should be awarded instead of the $900,00 plus interest that Justice Applegarth ordered Nine and Mr Cater to pay each brother in November.

The Wagner family's lawyer, Tom Blackburn SC, argued that the defamation in the 60 Minutes broadcast and that caused by Mr Cater's words were "very different".

The program was filled with "eerie" music and was relentlessly accusatory in tone, he said.

It also contained references to the deaths of 12 people and included the words "incomprehensible grief, trauma, and devastation" while insinuating concerns about the quarry had been hidden from the public.

"What Channel Nine broadcast was not merely Mr Cater's words but its own lurid and sensational overlay," he said.

"(The program) rose to a whole new level of seriousness, gravity, and pejorative meaning."

Mr Blackburn said it was also "outrageous" that Nine was appealing against Justice Applegarth's judgment on grounds not heard during the Brisbane Supreme Court defamation trial.

A full bench of court reserved its decision.

Australian Associated Press