Nonlethal and lethal damage is a tricky spot, so it's probably worth reviewing it as I understand it:<br/><br/>Basically, you fall unconscious from nonlethal damage when you take nonlethal damage that exceeds your<em>current HP.</em>Now if you only take nonlethal damage, then you have a nonlethal HP pool equal to your total HP. But if you take lethal damage, that decreases your current HP and thus the amount of damage you can take. See below for example:<br/><br/><em>Taken from the paizo forums (credit to DM_Blake for the explanation).</em><br/><br/><div class="spoiler_container"><div class="spoiler_header" onclick="hideSecond (this);" role="button">Spoiler: Click to Show/Hide</div><div class="spoiler_body">To illustrate, let's us a guy with, say, 50 HP.<br/><br/>In a bar fight, this guy gets punched for 5 non-lethal damage. He now has 50 HP and 5 non-lethal damage. He gets kicked for 8 non-lethal damage so he now has 50 HP and 13 non-letal damage. Then somebody shivs him with a dagger, sneak attacking for 30 real damage. This drops him to 20 HP with 13 non-lethal damage.<br/><br/>At this point, he is still conscious because he has 20 HP and his non-lethal damage is less than his current HP. Now a couple things can happen:<br/><br/>1. He could get kicked for 8 non-lethal damage. This would bring him to 20 HP with 21 non-lethal damage, whereupon he would fall unconsious because his non-lethal damage would exceed his current HP. <br/>2. He could get knifed for 8 real damage, bringing him to 12 HP with 13 non-lethal damage, rendering him unconscious because his non-lethal damage is greater than his current HP.<br/><br/>It's as easy as that.<br/><br/>Clearer now?<br/><br/>Don't forget that when your non-lethal damage is equal to your total HP (not your current HP), all further non-lethal damage becomes lethal. So, in your OP, if those 13 HP had been non-lethal damage instead of lethal damage, he would have taken 1 more point of non-lethal damage (bringing his total to 7) and then the remaining 12 points of non-lethal damage would have converted to lethal damage which would have left him at -5 HP with 7 points of non-lethal damage.</div></div>