Official comment
Personally, when I've used this configuration, I've done it three different ways:
1) Connect the CDJs to channels 1&4, connect the SP-16 master output to channel 2, and the AS-1 to channel 3. This gives you an independent mixer channel for each source.
2) Connect the CDJs to channels 1&4, connect the SP-16 master output to channel 2, and the AS-1 to the input on the SP-16. This allows all the production audio to be controlled via the SP-16, and then its master audio has its own channel on the mixer.
3) Connect the CDJs to channels 1&4, connect the SP-16 via the send/return, and select AUX as the FX type and return to channel 2. This is basically the same as option 2 (AS-1 can connect in either option 1 or 2), but you now have the ability to record samples from the mixer.