When you use the 0:1 addressing scheme, it will read read the first 8 channels from the AMUX-64T. It will store the data in a 2D array with 8 columns. If some of those channels are not connected, the signals will be floating. If you only need 2 of these channels, you would extract them from the array. This is the only way that I know of to read multiple channels with an AMUX-64T.
hope this helps.