In our database we have almost 650 downloads. Unfortunately many of these do not have a package size so where we display the size on the front-end there is no value.
You can use the template tag [package_size] in link template or page template. However, if it doesn’t work, please let us know more details. Could you please share related url to check the issue? If possible please also share temporary admin access in a private reply to check and resolve the issue quickly.