Suppose on the 1st of any month, the number of employees is 250. Employees joined during the month are 20, and employees who left during the month are 5. The total number of employees excluding those who left is 250 + 20 = 270. The attrition rate is calculated as 5 / 270 x 100 = 1.85%. In my opinion, the calculation shown in the Excel sheet is wrong.