This doesn't mean the application is full, but it does mean that you've already started another application for the selected term. Puget Sound only allows you to apply for 1 program per term.
In order to see if you've already started an application for the same term, go to the tab My Application and it will show any other applications you've started. You then have the option to withdraw the application and apply to a different program or continue the application you started.
In addition to the Puget Sound application, you need to submit a program-specific application. Details and timing will depend on your specific program and term.