I have no idea what that means.
The highest accuracy in any system can only be 100%, so less than 0.5% is very very poor.
I don't know where you found the question, but I taught the JAA syllabus for twenty years, including some time setting and verifying questions in the CQB at Gatwick.
I know of many flawed/invented questions in commercial so-called "databases".
Beware.