The Status for each package can be seen under the somewhat cryptic heading EIOM. The column we care about is under the M character, where each package is marked with one of the following:

To change the Mark, just press the key for the code you want (equal, dash, or underline), but if you want to change the Mark to * (asterisk), you have to press + (plus).

When you are done, use an upper-case Q to save your changes and exit the Select screen. If you need help at any time in dselect, type ? (question mark). Type a space to get back out of a help screen.