I agree, don't listen to the chart on here. If the doctor isn't worried than you shouldn't be either. I'm 36 weeks at 30 pounds gained and doctor is happy (I started out at 110). I think I was around 15 pounds gained at 20 weeks also.
I've been within the normal range my entire pregnancy, and this app keeps telling me I'm above average! I'm currently 37+3 and at last week's appointment I'd gained 29 lbs.
I wouldn't listen to the weight chart thing, I'm nearly 35 weeks amd ever since a set up this app it has been telling me av been gaining too much weight, av never worried as think it is probably better to be gaining to much than not enough.
I'm pretty sure at 20wks I too gained about 15 lbs, or 10lbs, can't remember. I'm 39wks now and only gained 30 all together and despite it being in range it says I'm above. Rude dumb thing haha as long as you eat healthy ore often than not and are consistently eating good portions I wouldn't worry about weight gain at all.