Question Can I assign the second ADAT inputs for 16 total inputs on the Konnekt 48

It is not possible to use the second ADAT input to achieve 8 additional inputs. The second ADAT input is used for either double sample rate, or the TOS link S/PDIF format. Please see the notes below taken from page 8 of the manual:
ADAT/Toslink I/O connectors: the optical connections carry either Toslink (optical S/PDIF) or ADAT signal. ADAT
  • At normal sample rate, 8 channels of ADAT is carried on a single lightpipe. Use the MAIN connector. 
  • At double sample rate, 8 channels of ADAT is distributed on 2 lightpipe connectors. Use both the MAIN and the 96 kHz connections.
  • Studio Konnekt 48 handles up to 4 input channels and 4 output channels of optical S/PDIF via Toslink.