30 h/week is considered full time by the immigration. It doesn't matter how your company calls it.
Part time is always calculated based on specific hours worked: 9h per week, 20h per week, or whatever is in the contract. "Part-time" doesn't necessarily mean 15h per week.
But it shouldn't matter to you. You work full time. Just make sure that they write 30h/week, even if they call it "part-time". It is full time for the immigration.