BP is challenging a January ruling over the size of the 2010 Gulf of Mexico oil spill as it seeks to lower its civil penalty for the disaster. BP faces up to $13.7 billion in federal fines.

The notice of appeal, filed Monday (Feb. 24) in New Orleans, comes days after U.S. District Judge Carl Barbier rejected BP’s attempt to lower the maximum fine for the spill.

Barbier ruled Jan. 15 that 3.19 million barrels of oil spilled into the Gulf of Mexico during the 87-day gusher. The ruling was based on evidence presented in October 2013 in the civil trial over the spill.

BP argued only 2.45 million barrels spilled during the disaster, while the federal government claims 4.19 million barrels spilled.

Barbier has not yet ruled on how much BP owes in fines under the Clean Water Act, the primary federal law governing water pollution. A ruling could come at any time.

It has been nearly five years since the April 20, 2010, Deepwater Horizon rig explosion, which killed 11 men and unleashed the worst offshore oil spill in U.S. history.

The civil trial involving BP and its partners started in 2013 and was split into three phases.

The first phase assigned blame for the spill and finished in April 2013. The second phase weighed BP’s effort to plug the oil well and sought to determine the size of the spill. The third phase, which ended this month, dealt with potential penalties for BP and Anadarko Petroleum Corp., a partner in the failed Macondo well.

In addition to Monday’s appeal, BP has challenged Barbier’s finding that the company acted with “gross negligence or willful misconduct” leading up to the disaster. Barbier made that ruling in September, triggering a maximum potential penalty of $4,300 per barrel of oil spilled.

BP says evidence presented during the oil spill trial do not support the finding. It has asked an appeals court to overturn the ruling.