How can word multiple documents just close the current window and not close all?

When Office Word closes, it closes only the current window, not all of it, and when you set an error in Office Word, it appears, and when you click the Close button, all the windows are turned off together, how do you set it up?

1, as shown, open two word.

2. At this point, you can see that the taskbar icon displays only one word icon, not two overlapping.

3. When you close, it's all closed.

4, click the upper left corner of Office icon, click "Options"

5, enter Word option, click Advanced, check the taskbar window

6, you can see the following into two icons, closed, it will only close one.