That is best handled using space-before/after for paragraph spacing, preferably in the paragraph style.

Can you explain to me how it works?

I assume this is in response to If you right-click on one of these numbers and pick "Paragraph" from the pop-up menu you will get a dialog box with settings for space before and space after.
If you select all of the numbers and right-click you can get the same thing.

This is best handled using a paragraph style so you can have consistent formatting that is easy to change for all things you want formatted the same way in a document.

Resources:

• The Importance of Styles in Microsoft Word
• Basic Concepts of Microsoft Word - from Shauna Kelly

If you are going to be using Word for your writing, both of those are worth reading.