The LFE output of a receiver is only one channel, the ".1" that follows the previous 5, 6, 7 or whatever number preceeds it.
The fact that they seem to have two, neither of which is labeled right or left, indicates that they might have provided the option for two powered subwoofers.
But without knowing the receiver (there are many different Sony receivers) you have, it's impossible to speculate.
But, I wouldn't combine the two without knowing what's going on inside the receiver. Just use one, either one, to the Bose.