I'm not sure about your school but here we have three grade types,
working grade, target grade and aspirational grade,
working grade being what you're working at, target grade being what you're most likely to achieve as a result of your working grade at the time or what you're working towards, and aspirational grade being what you yourself want to achieve in the final exam. Our individual teachers have learner conversations with us to decide on these grades.
I think your predicted grades are your target grades, but that sometimes changes every month when report cards come out. If you're working at a B and you want an A, your target grade will be an A most likely. But if you're working at a C or lower and want an A, our teachers will decide for us, with it usually being low.
sorry if this isn't much help, that's how it works in my school. We just have convo's with our teachers but depending on how well we do in the subject our target grades can always change, and we try to keep them high if we're wanting to get into uni