Render your video as MPEG-2 and your audio as AC-3. Check the total size of the two files. As long as they’re under the 4.3 GB. limit, you’re OK.
DVDA has a LONG history of incorrectly reporting the file size. As long as you know that you’re under the limit, ignore the warning and click Next. My guess (and it happens to me a lot too) is that DVDA will proceed as if nothing is wrong 🙂