First, by clicking long arrow a creature would move one field forward. After that the arrow would shrink. Then the player could use some other cards and eventually use the remaining moving point by clicking the arrow again.
In example below the player, who wants to get King's Rider in front of the building, would save one mana point by this change – would move forward in standard way and then use Maneuver ability intead of using the ability twice.
First, by clicking long arrow a creature would move one field forward. After that the arrow would shrink. Then the player could use some other cards and eventually use the remaining moving point by clicking the arrow again. In example below the player, who wants to get King's Rider in front of the building, would save one mana point by this change – would move forward in standard way and then use Maneuver ability intead of using the ability twice.