This story is another example that you should take to heart in your practice of training the mind. You have to be very, very careful. Don't let any Hindrances come in and take over your mind while you're practicing concentration. Don't let your monk run away from you, and don't you abandon your monk to go running after dogs. As for the goodness that comes from keeping track of your monk, it will send you to good states of becoming and birth, and will raise your mind ultimately to the level of the transcendent.
Wrong concentration is concentration lacking mindfulness and alertness.
Wrong release is when you get beyond distractions by falling asleep. Another form of wrong concentration is when you lose track of your breath and your body. You fall for these things and hold onto them as being trustworthy and true. A pure mind is one that has grown dispassionate to thoughts of past and future, and has no hankering for any sights, sounds, smells, tastes, tactile sensations, or ideas at all.