Exactly. If you have a match sheet, take a look at the column beside the team number for each station. At some point, the dominant letter (T, IIRC) changes (to an F, IIRC--I may have them swapped) for one match. That's how you know who the surrogate teams are and how many there are.
Funny story: In Arizona, I happened to be at Pit Admin for some reason and a guy came over from the pit display to say that his team was missing a match--they only had three showing, and played 4. Then someone else came up with the same thing, but remembered that it was the third match that was missing. The two teams had played against each other--and both were surrogate teams (the correct term these days--the placebos were hovercraft and vacuum cleaners back in the '90s

).
At that point, we figured out that it didn't mean anything in terms of ranking, and didn't have any other effects.
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Past teams:
2003-2007: FRC0330 BeachBots
2008: FRC1135 Shmoebotics
2012: FRC4046 Schroedinger's Dragons
"Rockets are tricky..."--Elon Musk
