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All the files from a package can be downloaded at once in form of a ZIP archive, which saves time in comparison to downloading each singe single file one by one. This sets the maximum file size for files contained in this ZIP archive - files larger than this limit will not be included in the ZIP archive and must be downloaded separately.
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Sets the limit on maximum total size a the package (meaning the sum of the sizes of all the files in the package).
The whole settings screen looks like this:
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