The default training methods for Attack, Strength, & Defence are shared xp through slayer. Your highest xp of these three skills is used and calculated at the shared xp rate. The hours for this are shown next to your highest xp skill. The two lowest xp skills then take into account the shared xp, and any remaining xp is calculated at the concentrated (meaning non-shared) rate, and the extra hours for these skills are shown next to their respective skills.