It pertains to the tools on Flores island -- the island was never part of the mainland in human times, and that's the age of the oldest artifacts found there. What we're expected to believe by the "land bridge" advocates is, it was a one time deal, and then no one thought to do this again until the settlement of New Guinea 740,000 years later, and in that part of the world, another 15,000 went by before anyone built another boat and went to Australia, and thereafter another 44,700 years went by before the next boat reached Australia.
Not familiar with any of this.
Off to Wikipedia for the basics, then to Google for more depth.