Your Matshita burner probably doesn’t have firmware support for the TDK media you are burning, so it only offers the lowest possible speed.
Try some other DVD media and see if those can be burned faster.
My Matshita UJ-840S hates most DVD media but I don’t know if your drive is as picky as mine. (It prefers Taiyo Yuden 16x DVD+R media).
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