Pregnancy weight gain

TH👶

I’m a plus size girl and pregnant with my first. I saw my ob for the first time yesterday at 8 weeks 1 day and she only wants me to gain 15 pounds the ENTIRE pregnancy. Is that even possible??? My sister gained 80 but she was crazy skinny to start. I plan to get a small treadmill soon to stay active everyday but that just seems unrealistic and I worry she may shame me if I gain more