[Game Play] Cinderhulk jungle items actually STACK with Sunfire Cape

Here is my actual test:

Use Garen, no mastery, no runes, bring smite but never use, no teammates, no buffs, never auto attacks.

Cinderhulk+Bami's Cinder:

At level 10, 84 magic damage VS Crimson Raptor (0 magic resist), 45 magic damage to minions, 32 magic damage to beginner AI Ashe(with magic resist 30)

Cinderhulk+Sunfire Cape:

At level 11, 108 magic damage VS Crimson Raptor, 108 magic damage to minions, 55 magic damage to 30 mr Ashe. At level 12, 56 magic damage to Ashe. At level 13, 58 magic damage to Ashe. 114 magic damage VS Crimson Raptor.

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Anyways, this stack is HUGE, especially Cinderhulk+Sunfire Cape VS minions, over 100 damage, and I have no idea why it is happening.