Second generation national insurance deductions

Does anyone know how the second generation NI contributions for part-time employees are calculated? My understanding is that if you earn over 23,800 ten you pay 1.91%. But on what amount? The full net income? Or only on the amount above 23,800? Or only on the 23,800? I couldn’t find a clear answer to this online.

As per understanding your part time employer and employees need to pay 50-50
You can also check with NHI webpage.

Thanks for that. I was actually asking about the amount liable for the deduction. I now gather it’s on the full net income. The issue of employer contribution is separate. In my case, I’m effectively paying twice as I want to keep up self-contributions because that’s tied to something else. Not complaining.