That's an LG burner, and ImgBurn automatically booktypes +R media on LG burners, provided that the burner supports it. Also, all newer burners booktype DVD+R DL media to DVD-ROM by themselves, so I don't think you need to worry about this. If you insert a burned disc the booktype is shown under "Physical Information (Last Recorded)".
Can you post a log of a failed burn? Look in ImgBurn's Help menu.