Adding a percentage magic path

[Hoplosternum]

I have been trying to do some moding.

I wanted to add a 33% chance of getting blood magic. So I used this command:

#custommagic 16384 33

This seemed to work as some of the units did indeed get 1 blood magic. But it seemed to be far less than 33%. Granted I only built a few (40 or so over two test games) but I probably only got half a dozen blood mages. I notice that most of the game ones are 10% or 50% chances. Are these the only percentage chances that work well?

I am also interested in giving a percentage chance for Holy magic, or rather a boost to Holy magic. I assume this would work in the same way as any other kind of magic path?