Spreadsheet programs have different cell types like General / Standard, Text, Number, Currency and Dates. Since the program does not know what type of data is in each cell, it tries to guess. In most cases it assigns the General or Standard cell type to each cell.
This cell type makes changes to numbers that are being imported. For example:
028263 will be imported as 28263 – dropping the leading zero. This is an issue when 028263 is the SKU for a product.
111222333444 will be imported as 1.11E+11 – converting the number into scientific notation. Scientific notation is used by scientists to display very small or large numbers.
To avoid the program converting the numbers, the CSV file will need to be imported rather than opened.
If you are using Microsoft Excel, check out this article:
If you are using Open Office, check out this article:
If you are using LibreOffice, check out this article:
If you are using Google Sheets, it does not give the option to change the cell format when importing: