Well if you can get yourself to not worry about the numbers you can try my method which in time produces amazing results. The theory: less is more with added resistance. What does that mean in English? Weighted Pull-Ups.
Get your hands on a belt, attach it to weights, and do them 2days a week consistently and increase the weight by 5lbs every 3rd week.
Start at 5lbs, and do 3x3 with 1 minute rests. I know it doesn't sound like a lot, but as the weight increases so does the difficulty, and in time 3x3 will be that more challenging, and after you get up to 50lbs attached, one day when you are fresh just jump on the bar and see how many you can do un-weighted. You will surprise yourself as long as you follow the previously suggested consistently.
There is more to this and what I do but for this topic that should cover it.