This symbol (the number of arrows) in the first grade of primary school mathematics indicates continuous simplification, which generally appears in the unit knowledge point of "continuous addition and continuous simplification" in the first grade mathematics, such as 24-4-4-4-4 = 0 (the "-"in this formula can be written as the number of arrows above) indicates continuous simplification until all the numbers are simplified. The application of this symbol makes the formula of continuous reduction easier.