No doubt about it, but Apple's Time Machine is a wonderful piece of magic, er software, that enables you to easily backup your computer and then easily see all of the files you've backed up.Trouble is that you can eat up a lot of your storage real estate by having redundant files upon files upon files upon files (just like all of those stacks).
Here's a link from Tidbits that helps you first see how much space Time Machine is using and then gives you the ability to delete unnecessary files, like ones that don't need multiple backups.
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