Problems with AD5941 Register.

Hi,

I am using AD5941 in my master thesis project and have problems when reading the datasheet, specificly, on page 126, table 173 for CLKEN1 register:

1. The 7th and 6th bits are 0x1 after reset, but the description says 'always leave at 0 and never write to these bits'. What does it mean? Isn't that a conflict?

2. In this register, some bits are reserved and other bits must be written at initialization (for example, the last 2 bits), is there a way to write only some of the bits instead of the whole register?

It will be really appreciated if someone can help me with this, thank you!