"I can't understand why you think for those 145 million in that case that forced arbitration is unfair, but in other uses in your company you think it's fair", he said.
Equifax said a forensic analysis of the event carried out by a cybersecurity firm had now completed.
However the number of customers hit in some markets may be less than previously thought - as the report claims that only 8,000 Canadians were affected, not the 100,000 originally reported. It was mentioned repeatedly by lawmakers at the hearing, which looked broadly at the breach, its effect on consumers and concerns about insider trading.
Former Equifax boss Richard Smith may have been the headliner of the Senate Banking Committee's probe on Wednesday into the company's massive data breach, but it was a photobombing Rich Uncle Pennybags who clearly stole the show. The flaw was disclosed in March, but Equifax failed to detect and fix the hole.
On Monday, Equifax said its breach potentially affected 2.5 million more people than it had previously stated.
Equifax offered free credit monitoring to affected consumers.
Smith retired last week.
Smith noted that in addition to his departure, the company's chief information officer and chief security officer also left the company following the breach.
The agreement was first reported by Politico.
"Given recent Equifax breach the IRS needs 2make clear &demonstrate that taxpayer information is safe if doing biz w Equifax", the Iowa Republican tweeted Wednesday.
Non-profit organization Public Citizen said they were the ones who sent the Monopoly Man to the hearing as a statement against Equifax's arbitration clause, which they say gives them "a monopoly over our justice system".
The recently departed CEO of Equifax faces a second round of tough questions on Wednesday from USA politicians eager to hear about what he and company executives knew about the breach - and when.
Smith made the revelation in a hearing before a Senate Judiciary privacy subcommittee, his third appearance before Congress this week.