Ixia, a maker of computer-network testing equipment, has announced that it is lowering revenue projections for the first quarter due to restatements of its results from prior quarters. The Calabasas company said it expects revenue of $121 million to $123 million in the quarter ended March 31, below its previous guidance of $125 million to $127 million. The company plans to announce its quarterly results after market close on April 30. The change reflects $4 million in revenue that the company had expected to recognize in the first quarter but has now been added to restated earnings for prior quarters. The company said its prior quarterly results “have been restated to correct certain revenue recognition practices, including with respect to an implied warranty arrangement with a customer.” The restated financials were included in the company’s 2012 annual report, which was filed April 4 with the Securities and Exchange Commission. It restated its first quarter projections after market close on Thursday. Shares lost 31 cents, or 1.6 percent, to close at $18.37 on the Nasdaq.