Hello, and welcome to the forum.
Assuming you are using FEI mode, the DCO frequency will be 1024 times the reference frequency. This frequency is then divided by the BDIV factor, and a further divide by 2, to give the bus frequency.
After POR the default BDIV factor will be 2, so that the bus frequency would be 256 times the reference frequency, i.e. a bus frequency between the limits 8 MHz to10 MHz after the internal reference has been trimmed to the required frequency.
The frequency tolerance for the internal reference, over the temperature range 0C to 70C is given in the datasheet (Appendix A).
Regards,
Mac