The reason paraliminals work so well is that Paul is a master of the "artfully vague" open ended languaging that allows enough specificity to get you on track and pointed in the right direction, but enough latitude to make it work for your own specific circumstances. Those of us who like to run everything through our logical, linear, pragmatic mind can find this frustrating.
As the manual specifies, Session B asks you to identify the objects or situations you fear. These will generally be more broad-scope and universal than the specific issue and/or circumstance you work with in Session A. The signal or issue you take to Session B can occur in multiple circumstances, such as being in large groups of people. Session A might be used before a family gathering in which you know you will have to interact with a person who always gets under your skin.
Don't get too hung up on the specificity or generality of the occurrence. Just set a clear intention of what you want to achieve, float down the middle of the two voices, and your other than conscious mind will take care of the rest.
As you continue to use the paraliminals, you will gradually develop an inner sense of what will be most effective for what circumstance.
To whatever extent you can, go with the flow, and allow things to evolve and unfold in their own perfect fashion and timing. You don't need to "understand" it, but to allow it to be whatever it is.