Why did the centaurians choose 982 megahertz for their signal to us? It is in the 33 cm band for one, and they probably also know we don't use that band much.
Why 33? I believe they understand the universal esoteric canon of numbers and measurement, including the MOST esoteric number 33, which, among other things, is the orders of magnitude above and below the human being (being 33 both above(the entire universe) and below(down to the Planck length))
As above, so below.
Don't forget the adult human being has 33 vertebrae in our spine. We are a fractal of the entire scale of the universe, with us being almost exactly in the middle, if not THE middle.
This shows me: the aliens use/know our measuring systems, which are built into the universe(which includes, yes, the metric system) which shows they probably use base ten as we do. This is probably because they are human as well.
Off topic, one fun fact I learned recently is that my name in gematria are the numbers 11, 22, and 33.
I had thought we were alone in the universe, but now I am rethinking that, have been rethinking that a lot lately.