The idea of time distortion was mentioned a couple times during the episode, such as when Riker said they were lucky they didn't end up across the galaxy in the middle of next week. I always assumed that they would have chalked up the difference between the ship's chronometer and official Starfleet time to distortions caused by the wormhole. But for them to have been unconscious much longer than the imaginary 30 seconds would have caused questions, since Data was supposedly unaffected and, as we saw, knew exactly what to do to revive them. Without the complication of a hostile force, 30 seconds must have been the approximate time it would have taken Data to analyze the problem and initiate the solution.
Although the precision of the 30-second response always bothered me a little. I thought Data should have either said something like "32 seconds" or estimated and said "about 30 seconds." After all, the crew spent a couple seconds in semi-consciousness on their way in and out.