what part is confusing you? disable makes it so it's disabled. stats show you impressions of that ad. the number is the weight-- which determines how often it's shown. if you have two ads, one with a weight of "1" and one with a weight of "2," the second will be shown twice as often.
Oh sorry I forgot to actually say which part I was confused about. And yeah I meant the select box. So it's just to determine a ratio between the sites you add to be shown on the network. Ok now I understand Thanks