AD7147 capacitance resolution confusion

Earlier in this forum, the AD7147 resolution was given as 24.4fF per count or about 1600 pf for a full scale 16 bit output.

Figure 18 in the data sheet shows roughly 60,000 counts for a 25 pF Cx or about 0.4 fF per count.

The specified input Cx range in the table is +/- 8 pF for a resolution of about 0.25 fF per count.

I'm having trouble reconciling all of the above. My application involves measuring the delta-C in approximately calibrated units (large scale offsets are not important).

Can someone clear this up for me?

Thanks,

tommy