Answer: The increase decimal and decrease decimal buttons change the number of digits after the decimal point for a selected cell or range of cells in Microsoft Excel.
These buttons are located on the Home tab of the Excel Ribbon, in the "Number" group. When you select a cell or range of cells that contain numbers with decimals, you can use the "Increase Decimal" button (which looks like a "up arrow" icon with a dot and a line) to increase the number of decimal places displayed in the cell(s). Similarly, you can use the "Decrease Decimal" button (which looks like a "down arrow" icon with a dot and a line) to decrease the number of decimal places displayed.
Note that these buttons only affect the display of the numbers in the selected cell(s), and do not change the underlying value of the cell(s). To change the value of a cell, you must edit the cell directly or use a formula to perform a calculation.