Multiple Positions

Is there any significance in the order of positions listed for players who can play several?

For example, I have a DMC/DC, but have also had players who were DC/DMC...do I take this to mean they are more effective in the first listed position, or does it mean nothing?

The first position listed is the first position they knew. So, if you train a player who is a DC to also play DMC, then it would show up DC/DMC. As far as I know, this doesn't mean they are more proficient at one versus the other.

Unless their statistics make them worse at one. For example, if you train a DC to also play DMC, but prior to this training had only improved his defensive and physical/mental chararcteristics, he is unlikely to be very effective in the attack (because his passing, shooting, etc. statistics will be poor).