If you rotate the comparison card, it is estimated that there is sand or other things between the disc and the Fiona Fang disc, and there are many gaps, right?
If you use it for study, you must buy a high-quality compass. I suggest you go to the medical clinic. Their compass is good, how to say, the quality is up to standard, and they have been making compasses for more than 30 years. You can look for it in Taobao.