mt-metis orderings for The University of Florida Sparse Matrix Collection

Hello,
I'm trying to use mt-metis 0.4.3 for ordering matrices from The University of Florida Sparse Matrix Collection. I call mtmetis_nd() with the default settings. Running mt-metis using 16 cores, I get orderings with 10-30x non-zeros more than 1-core results.
For example, for matrix parabolic_fem (http://www.cise.ufl.edu/research/sparse/matrices/Wissgott/parabolic_fem.html) mt-metis gives 26,530,942 non-zeros using 1 core and 564,678,524 non-zeros using 16 cores.
What should I do to improve the quality of orderings?

Thanks in advance