I've actually asked this before and its pretty much a combo. 20 publications in a sketchy 15th tier journal that publishes anything that comes their way obviously won't do much.
I basically heard > 6 "real" publications, not just CV padding, with at least a few first authored. Though obviously if you can crank out more, it certainly won't hurt your chances
I think 6 is a pretty reasonable goal and I'm shooting for quite a bit more than that though with the review process there's no real way to tell how long it will be before things are actually published. Obviously not everything has to be in Abnormal, but high-tier specialty journals, APA division journals, etc. Seems like alot of the faculty I know who attended one of those internships had their master's published in abnormal, which scares me, but its a biased sample so I'm not sure if that's a requirement or not