29.7mpg! Nah!!..

Today just to check outside temp I pressed trip comp. And I noticed that my mpg is 29.7mpg. I don't think it's correct. I'm a lead foot for the past two fill ups to test it's worst mpg. I am expecting 16-18 mpg but after 95 miles left for range this is the reading. There's something wrong.
One time also I am at the stop light slightly uphill(if that matters) and the mpg(the dynamic mpg clock) got stuct at 50mpg! Could this be it?

If that is the problem, it's a software glitch that needs to be checked. I'll make some phone calls tomorrow to area dealers in Austin, San Antonio, Houston if this is a known issue.