If you're currently running synthetic, don't even worry about it. The maintenance light is preset to I think 7k mile intervals. With modern engine technology + synthetic oil, people can safely and easily get 15k miles between changes (assuming you're not using a cardboard walmart filter...). Check your oil dipstick. If the level is fine, you'll be good until you get home and get your oil changed.
15% is a measure of the oil life. DO NOT ADD ADDITIONAL OIL, unless the dipstick under the hood of the car indicates it is more than a quart low, which it likely is not. When the oil is 15% you can drive until you get home to have it serviced, as long as it is not more than a quart low.
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