the second pass should take up to an hour. After this pass, you should be able to grasp the content of the paper. You should be able to summarize the main thrust of the paper. with supporting evidence. to someone else.This level of detail is appropriate for a paper in which you are interested. but does not lie in your research speciality.
Sometimes you won't understand a paper even at the end of the second pass. This may be because the subject matter is new to you. with unfamiliar terminology and acronyms. Or the authors may use a proof or experimental technique that you don't understand. so that the bulk of the paper is incomprehensible. The paper may be poorly written with unsubstantiated assertions and numerous forward references. Or it could just be that it's late at night and you're tired. You can now choose to:(a) set the paper aside. hoping you don't need to understand the material to be successful in your career.(b) return to the paper later. perhaps after reading background material or (c) persevere and go on to the third pass.