I just realized why your numbers are different than mine (i.e. higher).
Click the Settings box in the lower left corner of the calculator.
Now click the 1 kilobit = 1024 bits option as shown below. I can’t remember what the rationale was for choosing this setting but it always works for me.
My guess is that using the slightly lower numbers will finally worj for you.

BTW, there are times that DVDA will say that the file size is too large even though you know that you’re under the limit. If that happens, ignore the warning and DVDA will happily prepare your DVD for you 🙂