Complex sentence: As for Chen Xuanfeng and Mei Chaofeng, they started practising the skills in the manual but interpreted wrongly the underlying principles and mastered an unorthodox version of a skill known as the Nine Yin White Bone Claw (九陰白骨爪).
Split into simpler sentences: As for Chen Xuanfeng and Mei Chaofeng, they start practising the skills in the manual. However, they make a wrong interpretation of the manual's underlying principles and master an unorthodox version of a skill known as "Nine Yin White Bone Claw" (九陰白骨爪).