Your GP training term is determined by your RTO’s assessment of your progression through the AGPT program and is dependent on both completion of 6 months full-time equivalent (FTE) accredited training and satisfactory progression of performance on educational tasks and assessments.
Your RTO will determine the amount of your part-time training that is actually counted towards accredited training. Most RTOs will pro-rata your progression through training so if you are working 0.75 FTE, your time as a GPT1 will simply be extended until you have completed six months of 1.0 FTE total.
However (for example) some RTOs will only count 0.5 FTE of part-time training towards progression, even if you actually work (and are paid) 0.75 FTE.
The key point is that you progress from one GP training term to another (and with that, your base rate of pay will change) when your RTO assesses you as having met requirements, rather than just being a GP registrar for six calendar months.