Well, im not sure if this a bug or my math is just so wrong. So my offline gains before using 6 pre runes is 82%, and after i put 6 PRE runes with 2% offline gain for each runes + 20% offline gain from runewords,
82% + 12% + 20% = 114%
But somehow i online got 102% offline gain in total. Again, i dont know how this offline gain calculation works, im just posting this so someone can enlighten me.