I had a look at the LTC6904 datasheet and also the user manual.
I'm with you on the address, 0x17 is the correct value to give the Wire library. But there is an address pin (ADR, pin 4) on the chip that can modify this. With a low value on pin 4, 0x17 would be the address, with a high value on pin4, 0x16 would be the address. The user manual indicates this is set via a solder jumper on the board.
The module is sent a count that sets an oscillator frequency. That frequency is determined by the high 14 bits of an unsigned word. The two MSB enable or disable the two clock outputs.
I think you meant the two least significant bits?
Serial Port Register Description
OCT[3:0] – Frequency Divider Setting. (See Frequency
Setting Information Section)
DAC[9:0] – Master Oscillator Frequency Setting. (See
Frequency Setting Information Section)
CNF[1:0] – Output Configuration. This controls outputs
CLK and CLK according to Table 2.