Not correct.
You increase the input impedance and create 10x attenuation by adding R1 = 9MΩ in series, not by adding capacitance.
The impedance of R1 is approximately 9MΩ but not quite. R1 and the probe cable both have capacitance and inductance.
The impedance of R1 increases with frequency.
The purpose of the capacitance C1 in parallel with R1 is to reduce the impedance with frequency. It adds back the high frequencies that were overly attenuated. This capacitor is a trimmer capacitor and it allows you to adjust the impedance at high frequencies. That is why it is called HF compensation adjustment.
You increase the input impedance and create 10x attenuation by adding R1 = 9MΩ in series, not by adding capacitance.
The impedance of R1 is approximately 9MΩ but not quite. R1 and the probe cable both have capacitance and inductance.
The impedance of R1 increases with frequency.
The purpose of the capacitance C1 in parallel with R1 is to reduce the impedance with frequency. It adds back the high frequencies that were overly attenuated. This capacitor is a trimmer capacitor and it allows you to adjust the impedance at high frequencies. That is why it is called HF compensation adjustment.