Regarding Current and Voltage channel ADC of ADE7953

In the datasheet of ADE7953 it is mentioned that the ADC output swings between  -6500000*LSB(decimal) to 6500000*LSB(decimal). It totals up to 13,000,000 digital values but as the ADC output is 24-bit data-word which corresponds to 2^24 = 16,777,216 digital values.

So, where are the rest of 16,777,216 -13,000,000 = 3,777,216 digital values are being utilized?

Thank you

Regards 

Satya Prakash Singh