For PSLF, you are generally considered to work full-time if you meet your employer’s definition of full-time or work at least 30 hours per week, whichever is greater. Even if your employer does not consider 30 hours per week full time, they can select full-time as this is only for PSLF requirements.
For more information, visit Federal Student Aid: https://studentaid.gov/help-center/answers/article/what-is-considered-full-time-employment-for-pslf