pixel_player193531891 when you place a bamboo pillar in your camp it "costs" 4,000 bamboo and you will receive 2,720,000 XP (that's 680 XP per bamboo). When you empty the repeatable "bamboo forest" you receive an average of 37.14 Bamboo => 37.14 x 680 = 25,257. It is just statistics 🙂
