Basically, he "erases" time for up to a dozen seconds. To everyone else, time "skipped" forward, so if they were watching a movie they'll suddenly be ahead, or see a few bites taken out of their pizza.
To him, the next dozen seconds of movement of whoever's in super close range will show up as afterimages in that erased time, so when his power ends, he'll already know what they''ll be doing in the next dozen seconds.
At least, I think. In layman's terms, he throws whoever he's using the ability against into a pocket dimension, watches what they'll be doing in the next dozen seconds, and then acts on that information once the power's over.