How do i auto populate a field/value based on the dropdown?

[Tiger1]

I have a dropwdown menu that shows the value after the user selects the field in the dropdown menu. However, i do not want the user to then have to click the value shown:

Before the user has chosen value from dropdown menu:

After the user has chosen the value from the dropdown menu:

I do not want the user to have to click (4324) from my example above. I wan that value to automatically be chosen