I am just about to use Snapnames for the first time next week on a domain, so I'm not an expert, but I think I know the answer.
Search the domain you want on the homepage and let it come up in the results, then left of the name you can see a number how many other people have backordered it. You can't see this information in your control panel once you've already backordered it, you can just see it in the results.
Unfortunately the one I want has a load of people bidding, naturally. GL