I have both a "GOES Membership Number" and a "Membership Number / PASSID". I use the "GOES Membership Number" to login to the GOES website. After login this number appears as "GOES ID" in the upper left corner of the webpage. The "Membership Number / PASSID" appears on the "Trusted Traveler Program" line on the web page.
The last 2 times I departed from ATL, I have tried to use the Pre-Check program. The first time, I entered my "GOES Membership Number" in the TSA field on the Delta Itinerary page. The number was accepted with no feedback, but I was not allowed into the special screening line.
Second time, I entered the "Membership Number / PASSID" in the same field. Again, number accepted with no feedback, but it worked this time. Absolutely no waiting and no hassles at security, well worth the effort to figure it out.