Recently got tested for hiv ab/p24 with reflex test 6 months after sex, it came back as nonreactive(negative). but they have written - direct relationship exists between the hiv antibodies and/or p24 with num of rlus detected. what does that mean?

You're over-searching the web and misunderstanding something. Your negative test result proves with 100% certainty you do not have HIV. The index value (relative light unit, RLU) makes no difference as long as it is below the cut-off value for a positive result. (If positive, the RLU may be a rough indicator of viral load, but means nothing if below the positive value.