Everyone keeps saying she's going to come sooner....

So today I'm 34 weeks. Due August 13. Everyone keeps looking at my belly and saying she's gonna be a July baby. How do they figure this?? It's my first child, first pregnancy and I just don't know why ppl keep saying this when its not what I want or am hoping for. I was to carry to full term, despite the discomfort, bc I want her to be healthy!! Does anyone else get this kind of feedback about their due date based off their bump size!!??