Can't set the size of tags

I’m having a problem with a book exercise

Open the disclosure triangle next to
Tags. Set the Size of Tags to 7 and
enter the tags shown in the left image
of Figure 30.7. Note that in the
middle of your typing the name of Tags
Element 5, PowerUpBox, you may receive
a console message (“Default GameObject
Tag: PowerUp already registered”),

This is how it should look:

And this is what I got:

The problem is, that I don’t know how to set the sizes, I just simply can’t find the way. How can I set the sizes of the tags?

Your book uses an older version of Unity.

Just press the little “+” symbol under “The List is empty” and add your tags here, one by one.