How do you know which resonant frequency of the cantilever is the proper one?

Hi, everyone.
I'm quite confused. It's a rectangular beam,with one end fixed. Then I do the eigenfrequency study. When I apply different mesh method to the beam, for example, first I use Free Tetrahedral mesh to simulate.Then,in the second study, I use Free Triangular mesh on the bottom boundary and swept the whole domain. The difference of the resonant frequency between two study is about 70000Hz. Is this usual? The resonant frequency of the cantilever with same size and material should be the same right?

Thanks a lot. Looking forward to your reply.