At this point, the Kepler - Attachment fields | simple & multiple custom field is ready to be used as follows:
Step 1: Click on Attach file Icon 
to select a file.
Step 2: Choose a File from the opening window.
Step 3: As depicted in the screenshot below, some information about the uploaded file is available:
...
Case 2: The file size is greater than the defined one.
Case 3 : The attached file is empty ( file size equals 0 KB) differently from the configuration.
