That's a good catch on the Movement. Movement was added to the monsters with the intention of designing effects based on it, but these haven't been included in a set yet.
DIAMOND 2 + CIRCLE 1 = CIRCLE 3 This means that if you have a card that adds a bonus to your attack, you can add it even if it's a different attack TYPE (Standard or Counter-attack) and the resulting attack is a Standard attack rather than a Counter-attack. They have to be the same attack FORM, though (Melee, Magic, or Speed).
I read the original rule on this several times and similarly didn't get it. The explantion didn't help either. I can't help but seeing that as a rule that says you can combine two different things as long as they are the same. Can you give an example?
P.S. I notice that the rule is missing from the non-official new rules.
There are no cards currently that utilize monster's speed, but it was important to complete the stats for the monsters. The optional rules include a feature called "wandering pack" which utilizes speed (the stat is called speed, not movement).