Calculation of Parameters of AD9858

Hii,

Hope Everyone is doing great!!!!

Here my output frequency range 140 to 200MHz, and my Clock to DDS is 950Mhz , Can i know how i can calculate the DFTW,DFRRW, ,I have gone through the AD9858 datasheet  in pg:18 they given calculations but i am confused what value of 't' i should take.

Best Regards,

Prashanth