Typically, a root-position triad has nothing in the figured bass; if the text is really specific, it will provide "5 3" as the figures. But in this case, they've taken it one step further: they clarify that two pitches will be a third above the bass.
This is because of the voice leading from the prior chord. Since the prior chord is a V65, that means that the chordal seventh, D♭, will need to resolve down by step to C. And since the soprano moves from B♭ up to C, this means that two separates voices will be on C, and thus the uncommon "3 3" figured bass.
Nevertheless, this is still a root-position triad, so there is also an implied "5" in these figures. In other words, in addition to the two thirds (C) above the bass, there will also be a fifth (E♭).