It really doesn't tell you how good your English is, I agree its only concentrate on Grammar. Depends what you want to use the English for. If its for communicating with foreigners then its not much use as its not everyday language.
You correctly answered 14 of 20 questions.
[ 14 question(s) you answered correctly, and 6 question(s) you are wrong. ]
Your level is approximately 中學3-4年級 .
You correctly answered 17 of 19 questions.
[ 17 question(s) you answered correctly, and 2 question(s) you are wrong. ]
Your level is approximately 中學5-6年級 .
You correctly answered 12 of 20 questions.
[ 12 question(s) you answered correctly, and 8 question(s) you are wrong. ]
Your level is approximately 中學1-2年級 .