He's telling you "she needs to be 2 when she calves".....or what? She's gonna die if she doesn't have her first calf at 2? Be permanently sterile? Grow a second head?
Always beware of owners of intact male livestock of any species who want to use your female animals simply as a walking uterus.
I like mini Herefords myself, but I just can't see the point in that cross. Yes, his bull has testicles and I'm sure he'd cut you a great deal on breeding. But what is the offspring going to be? Besides cheap? Half large, half mini, part meat, part dairy, sounds like a mixed mess to me. If you want meat, breed her to a full size meat bull. If you're looking for another dairy animal, breed her to a dairy animal. I guess if you're wanting to breed down in size you could go mini, but I'm still not seeing that the offspring is going to be good for much. You could do better paying a bit more for a stud or AI fee and get a way better quality calf.