This exercise is a good one for helping clients who do not have a strong sense of their values. Rather than needing to 'know' which value is important to them in order to behave, is it possible to behave for a while to learn from direct experience how it feels to a) commit to behaving consistent with a freely chosen value, and perhaps b) learn over time which values may have meaning for the person? Some work with the client around this issue (e.g., willingness, defusion/letting go of 'needing' to know the answer) will be helpful. My experience is that it's a good idea to assign this as homework for an extended period of time -- at least a few days, a week or two, or longer if possible -- to help the client build up a longer history of behaving consistently with this value before coming to any 'decisions' about continuing to move forward in the direction of that or another chosen value.