How accurate is the data rate of ADF7023?

How accurate is the data rate of ADF7023? I know that it can be varied in steps of 100bps, but what is the maximum error/deviation in the 'actual' value from this 'setting value'. I had set the rate @19200bps for GMSK (i.e value 0xC0 in bbram reg. #0x10C) , but when I actually measured it in matlab, it comes out to be 19213bps, which shows a very high drift(677ppm) ! Please explain.

Also, which clock is used to realise this data rate? Is it the 26MHz crystal or some other RC oscillator?