I can't imagine anyone would stay in the lab for 4 years doing only what we would consider worthy of 1 point. Research assistant usually means the general scut work of placing orders, making gels and solutions, keeping the place tidy, etc. In clinical settings, it is the person who distributes & collects questionnaires, or interviews subjects without any input as to the science being done.
If you have some responsibility for the scinece, keeping a lab notebook, troubleshooting, consulting with the principal investigator, etc, then you'd be at 2 points. I don't recall if having a research grant that provides you with a stipend is a 2 or a 3, having done a poster or a presentation anywhere is a 3 and a publication in a peer-reviewed journal is a 4. This is a quick & dirty way to classify appliants according to the level of involvement they've had in research. An adcom might do the same in classifying leadership, clinical exposure, community service, etc depending on what they value in an applicant.