what does the number of hashtags define???

Hi Asmaa, The hash symbol represents a placeholder for digits but only if they exist. If you have 2 hash symbols in your custom formatting and the content of the cell is the number 1, only 1 will be displayed. However, if you use 00 instead of 2 hash symbols, Excel will display 01 because 0s are not flexible like hash symbols. Basically you use # to tell Excel that you want to display a number if it is available. Best, Ned