HIV duo 4th gen (CMIA) Of masturbation!

I did hiv duo 4th generation (SERUM CMIA) test and I got the value as NON-REACTIVE(0.04). I didnt had any sexual relationship but I went to massage centre and she did blowjob. it had happened on 18-Jun-2016 and I did the test on 29-Sep-2016(nearly after 100 days). 1. what my test value exactly tells? 2. what is cut off value. some website saying it is 0.25(the website says if less than 0.25 then it is most definitely negative band and if the value is near to 1 like >0.9 the value comes during window period). please confirm is this true? 3. give me description about HIV DUO 4th generation SERUM CMIA test? 4. Also, I got dark black line in my penis but I didn't had any pain. what is the reason? will it come because of masturbation