Here is a slightly old article from here at cdfreaks about bitsetting:
Some newer dvd drives will bitset +R disks automatically and some will only do it automatically for dual layer +R disks. Some can have modified firmware to add bitsetting, as the article states. And there are software solutions as well. ImgBurn for example can adjust this setting for several different makes of dvd burners, such as Samsung, LG, NEC, Lite-On and others. And there are other tools to achieve this, depending on your burner. Which is why I asked which burner you are using.