A "good" MCAT score depends on a number of things--including what kinds of med schools you're aiming for and your state of residence. (Some state med schools have strong in state preferences. Some less populous states have less competition for in-state admission.)
Here's aggregate data for 2009-2011: https://www.aamc.org/download/161690/data/table17.pdf
If you'll notice the median MCAT score has been rising steadily for the past 3 years and is now at 31.1 for all matriculants. And remember this data include the MCAT scores of students in guaranteed admission programs.
In general, one should aim for an evenly balance score across all 3 sections. The verbal score is particularly important. You should be aiming at a minimum of 10-11 in each section.
One section of one practice MCAT exam tells you nothing about your potential score. You might have gotten lucky on the question selection. (It does happen.) IOW, don't get too excited by your practice results. They don't mean anything yet.
Also as an aside, practice exam results tend to be higher than actual exam scores due to a variety of reasons--usually by 2-3 points.