SSC does not "modulate" the sense clock. It only spreads the clock frequency based on an LFSR. The spread spectrum frequency range must be within +/-10% of the sense clock frequency. This is taken care by the component and the component will allow you to choose the value only if this condition is satisfied. Please refer the component datasheet for details on the conditions required to be satisfied while choosing SSC.
Spread spectrum is center spread with center frequency equal to the sense clock frequency set in the component.
In the CSD (Self-cap) setting, the switching signal period on the sensor measured under the following conditions was 21.12us to 21.24us.
Modulation Clk 24000KHz
It looks like it is the same as the Direct waveform.
Are there any other settings required to enable SSC?
There are two conditions that need to be satisfied for SSC to take effect.
In the present configuration, condition 2 is not getting satisfied, as resolution, N = 14, mod clock = 24000kHz, SSCN = 7 and snsclk = 46.88.
Please make sure that the configuration satisfies the condition so that the component sets SSC correctly. If this condition is not satisfied, the component switches to Direct by default.