[Elecraft] KSB2 set up filter question

[Jerry]

Just finished installing the SSB adapter into my K2 (#4472) and on page 20 step 3 it says to set up my filter exactly as shown in Table 3.
My question is . Why do I have to change the ones for CW and CW reverse?   I guess I just don't understand how these filters work.   I plan to run mostly Digital modes,  but will use Voice occasionally.

Thanks in advance.

Jerry, N2UZ