According to MyUnisa, the year mark is calculated by four assignments (of which only 3 count towards the year mark) with the following weights Ass 1(0) Ass 2(30) Ass 3(30) Ass 4(30). This means that assignment 1 counts for nothing while the remaining assignments have a weight of 90/100.
If you have registered for modules and you open the link to the assignments, it has a link at the bottom left for the year mark. The issue is that the year marks only reflect the weight per assignment but it does not reflect the overall score. All due respect, weighting in any IT solution must indicate the total or the weight will be assumed to be out of 100 (percentage).
The purpose of having such a function on the MyUnisa site is to make it easier for the student to have an overall view on the status of the assignments. When unreliable, the student will have to his\her own record of the assignments and the weighted contribution to the year mark by examining the TLs. Maybe its just me, but my perception of having something with a particular score (in this case a percentage or credits) and giving it a weighted count is different from what has been reflected.