Gas in my oil

Hello I drive an automatic 2006 Jeep commander with about 233,500 miles on it. I just recently bought the car and I just did an oil change on it and put in its 6 quarts that it needed, now a week later the oil level has risen and it has a gassy smell on the dipstick. What could cause this to happen?

(when I did the oil change there was also gas in the oil pan)