What is part time hours?

I have been working at a company for almost 3 years. I recently started going back to school and only working part time. I was always told that part time employment was less than 32 hours a week. I only work about 24 to 25 hours now. They just told me that part time employment was less than 1000 hours a calendar year. And if I continue with working this amount that I would not be considered part time that it would be full time since it would be over 1000 hours a year. I thought if you had 1000 hours then it was considered one year of service not full time. They want me to only work 15 hours or less a week so I do not go over 1000 hours a year. I do not think this is correct. And who can live off of 15 hours a week. This would not even pay for the gas to get to and from my work. What is part time hours?