Most likely the dealer adjusted your chain at the first service. I used to work at a moto dealership and that was something we always did to new bikes at their first service. Always. I've adjusted mine twice, once very early on and again at around 4,000 miles. After the initial stretch during break in, you usually won't need to adjust it again for quite some time. Keep it reasonably clean and lubed and a chain will last a very long time.