The sequencing ADC switches between several inputs sequenced to convert all values one after the other.
The conversion rate is what you want to have, the actual conversion rate is what you get. Because needed clock is delivered by dividing your HFCLK by an integer ratio there is always a difference between them both.
Thank you bob.
One more thing i wanted to ask is why there is conversion mode option in case of delta sigma ADC where as SAR ADC does not have any such conversion mode.
The delta sigma ADC has a filter integrated which needs to be cleared when the input is switched from one signal to the other. The (sequencing) SAR ADC handles that internally, so there is no need for different conversion modes. Nonetheless are settings available to average the conversion results (which acts as a noise filter).