Basically, I don't know.
In midi, anything CCxx usually means a Control Change, i.e. one of the controllers.
However, CC55 is not a usual controller in it's own right. There are a block of 'Continuous Controllers' which are 'undefined' as far as midi is concerned, which usually means that they are available for use by specific devices as defined by said specific device. However, 55 is for the least significant part of CC23, and therefore would be unlikely to be used apart from CC23.
However, as these controllers are 'undefined', there may be certain devices that do use them for their own purposes. If, as you say, these connectors are outputs, there may be something that can use a CC55 input (but if so, what about CC23 ??). Maybe something else in the Analogue Solutions range can make use of this?
I'd suggest that you don't worry about it unless you have something that can use it?