AD9542 : Question about SOURCE PROFILE Register

Hello,

I have a question about SOURCE PROFILE register of AD9542.
The SOURCE PROFILE 0 to 3 are settings for reference input each.
I could understand how to use these.

The SOURCE PROFILE 4 and 5 are settings for NCOx , and SOURCE PROFILE 5 and 6 are settings for DPLLx.
They has same parameters as SOURCE PROFILE 0~3.
I can not understand why these registers has same parameters as SOURCE PROFILE 0~3.
What purpose of these registers ?
How to use these SOURCE PROFILE 4~6 registers ?

Best regards,

y-suzuki