0x52h is Synth_Denom (Denominator). You can select 128 or 125. Then in Synth_Num you can choose the numerator to get ratios like 96/128 or 96/125 ..... This is when you use the audio ports and want to generate the master clock (CLK_Master) it allows flexibility in the clocking output. Please look at pgs 52-56 in the data sheet for the other fields that are needed to configure the parts to generate the clock when configured as master. To configure the port as master you do this in 0x50h bit 3 Clock_MS.
For 0x00h OVR this is override. It allows the digital ports and clocks to be used when the part is in shutdown allowing for example the digitial mixer to be used when the analog blocks are shutdown. Please see page 32 of the datasheet for information.