How many pounds you can drop and how quickly really depends on how much you weigh now, your metabolism, your diet, your stress levels, and your activity. It probably also depends on your gut bacteria and your genetics.
But what I do know is that going on a crash diet to see how much weight you can lose in X number of days is never a good idea. As I say to my clients, most people can lose weight, but keeping it off? That's the tough part. If you overdo it, your body will fight you every step of the way to gain that weight back as quickly as possible. You'll also likely burn muscle mass in the process, which is not good.
So how much weight should you lose in a month? Its more simple than you think. Its the amount of weight loss that you can sustain without being miserable. That means not killing yourself with exercise, and not starving yourself.
It also means not having to turn down social invitations because the food doesn't fit your diet, and not being mentally tormented by restrictions and rules. In other words, no pulling a Jack Dorsey and fasting for days on end.
The right amount of weight to lose in a month is the amount you can keep off and still live your best life. A common estimate is 1 to 2 pounds a week, but again, it all depends on the factors above.