I don't think that is too bad
If the fluid didn't look metallic then you are probably O K. You will always get some metal paste at first, produced with new trans. The magnet was in trans? from the factory? I put a magnet in my trans at 60k and at 85k when I changed to different fluid there was no metal paste on magnet but the oil is very metallic, I would assume from sycro wear not bearings and it operates fine to the best of my knowledge.
Craig