[05CGMSTi]

How long did you watch the gauge before you started putting more gas in it? Subaru's have pretty slow fuel sending units, so it can take a min. for the gauge to register full after you fill it up. Another tip:never continue to put fuel in the tank after the pump has stopped. Because of the fuel vapor control system on the car, there needs to be an air gap in the tank for it to work properly. When you top off the tank fuel can get into the fuel vapor vent valve and damage it, triggering a CEL.