With 10 enemies in a cone in front of Shyvana, at rank 5, all enemies in a cone in front of her will take 200% of her auto-attack damage from Twin Bite. In addition, Tiamat's passive will splash half of that damage (100%) to each nearby enemy. This will be triggered 10 times (once for each enemy in range), but a target won't take their own splash damage, meaning they will be hit by 9 of the Tiamat splashes each. As such, every enemy in the cone will take 200% + (100%x9) = 1100% damage from Shyvana's Twin Bite attack.