As I understand it, if you use multiple filter conditions in a HCWP, the conditions are evaluated as OR's when filtering on the same parameter (e.g., Title = ABC OR Title = XYZ), and the filter conditions are evaluated as AND's when filtering on different parameters (e.g., Title = ABC AND Created by = Current User).
It appears, based on my limited testing, that this filtering logic also applies when filtering on multiple managed properties. In this instance I want to filter on RefinableDate00 and RefinableString00. Since these are different managed properties, I was hoping they would be evaluated using AND logic (Date is after [Today] AND String = ABC); however, it appears that the conditions are instead being evaluated as OR's (Date is after [Today] OR String = ABC). I think Microsoft should upgrade the HCWP to allow users to specify how multiple filters should be evaluated.