you have a 15.9 gallon tank so assuming your tank is divided into 1/6th as the has marks indicate then you would have approximately 2.65 gallons or whatever that number is left once the low fuel light comes on....HOWEVER, there is also a "2 gallon reserve" tank, as the owners manual states...so technically you have 4.65ish gallons left....

just going off what the owners manual says.