The main points are different, both of which can mean that now translated into Chinese is "Xiao Li is studying in the library."

But ... Move it. ます 1 Habitual actions such as Mori んはきます. {Daily} Habit formation state

Future actions such as Yoshida's visit to China next month. Planned future action

The current action is like Li Library's reluctance. Describe the current state.

The key is that people maintain a certain state, that is, people are in a certain state of action.

. . . Move in middle+ます

What's going on now is that Li's operation is continuing.

Emphasis is placed on the progress of the action, that is, people are doing an action.