Question about EVAL-ADL5569 board

Why does the resistors (R1,R2,R3,R4,R23,R24,R25,R26)  should be 35.7k in the schematic of ADL5569 Evaluation board?

To provide the input impedance match, I thought R1,R2 should be 0 and R3,R4 should be 50 (for differential input), which is far away from 35.7K.

Also, is the default configuration of this board designed as single-ended input or differential input? Do we need to change the resistors value to use it? 

We haven't bought this board yet, but hope we can know more information about it.