in the database, you need to set the download count column to use a numeric data type, and you need to set the download count column to have a default value of 0.
when the user downloads the file, the download behavior will be able to increment the 0 value to 1 and so on. But only if there is a default value of 0. If there is no value, the increment cannot happen because it will be set to NULL, math cannot be performed on a NULL Value.