How do UMS marks work?Watch
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Snab A Edexcel ( Salters and Nuttfield) Biology
It sounds as though you are in England taking linear A levels. If this is the case then forget you ever heard of the acronym UMS. It applies only to modular qualifications and all GCSEs and A levels in England are now linear. For linear A levels you see the mark you actually scored on the paper.
UMS was a feature of the old specifications, where the raw marks would be scaled to a uniform mark, and the grade boundary was for a fixed UMS - 90 for A*, 80 for A, etc. Now the grade boundaries are decided purely by the raw cumulative mark, and your AS exams don't count towards your final grade.