Fiorina insisted that the data did not reflect the entire financial picture surrounding the merger between the two companies.
Her testimony came on the first day of a hearing prompted by a lawsuit filed last month by Walter Hewlett, a dissident HP board member seeking to block the merger.
The documents suggest that internal sources at HP knew the merger would lead to greater losses than first believed and that, instead of a 12-13% accretion rate for company shares there would actually be a 10% loss.
In his opening remarks, Hewlett's attorney, Stephen Neal, said that the documents indicated that HP's management knew there were financial problems with the merger but they did not tell shareholders.
He added that even though they were aware of this, they were appearing on television and meeting with shareholders and analysts to assert the merger figures released last fall were, more or less, correct.
Neal buttressed that argument in his opening remarks by releasing an excerpt from Compaq CEO Michael Capellas' personal journal where he questioned the success of the merger.
Fiorina said she expects to be about 13,000 layoffs after the merger, not the 15,000 the company originally projected. She went on to say that she expected about 10,000 jobs would be eliminated because of duplication.
But, she added, the combined company was likely to end up creating new jobs, perhaps reducing the number of layoffs.
Neal is expected to eventually focus on HP's relationship with Deutsche Bank. He said documents show that Deutsche Bank's commercial side had gone to HP and asked to help it with the merger. They also show that Deutsche Bank would have received a $1m success fee if the merger went through.
Despite this, other Deutsche Bank managers had, originally, cast the bank's 25 million shares against the merger. It was only after Fiorina and HP chief financial officer Robert Wayman made a last-minute pitch to the bank in a conference call that it decided to switch 17 million shares.
Bank managers working with HP and those overseeing how the bank would vote were present, and Neal has suggested that there was an erosion of the "ethical wall" between the two groups.
Earlier, Hewlett's lawyer pointed to journal entries made by Capellas in which he wrote that the merger would be a case study for business students for years to come and that under its "current course and speed, we will fail".
Neal went on to present a variety of documents which, he said, showed an internal HP/Compaq committee had a much bleaker financial outlook on results of the merger than those made by managements' public statements.
HP's attorneys contended in their opening statements that those documents were out of context and purposefully conservative.
In addition to Fiorina, Wayman and HP board member Phil Condit, who is chairman and chief executive of Boeing, are scheduled to testify in the trial to determine whether HP's management tried to buy the votes of Deutsche Bank.