What does it mean for a man to sit in an official library?

It shows that this person has the foundation of being an official.

In ancient times, men went out to be officials, while women sewed clothes with their children at home, so they were rarely able to be officials in the court. So it is suggested that this person is probably an official here.

This is a folk saying, and many superstitious people believe it very much. Of course, if you want to have high rights and a certain status now, you need to be down-to-earth and get it through your own efforts. The answer is for reference only, please don't be blindly superstitious.