We need to be aware that there are two genomics coordinate systems: 1 based and 0 based. There is really no mystery between these two. You EITHER count start at 0 OR at 1. However, this can make confusions when analyzing genomic data and one may make mistakes if not keep it in mind. The TWO systems See the figure below to understand the two systems. credit due to Vince Buffalo from his book Bioinformatics data skills.