Q: Storage Issues with Photo Library

I brought over the Photo Library from my back up.

How did you do that?  Did you restore the Photos Library from the backup by entering Time Machine?

and look at all the photos/videos, it only shows 5GB of data.

Is that what the Info panel is showing, when you select the Photos View and open the Info panel?

After restoring a Photos Library I would repair it as described here: 

https://help.apple.com/photos/mac/1.0/index.html#/pht6be18f93

Important: You should back up your photo library before repairing your library.

 

• If Photos is open, choose Photos > Quit Photos.
• Press Option-Command and double-click the Photos icon in the Applications folder (or click the Photos icon in the Dock).The Repair Library window opens.
• Click Repair to rebuild your photo library.

Make sure, Photos is opening the library you restored and not a default library it created in the Pictures folder.

You can see the path to the library in the Photos > Preferences > General: The first line is showing the Library Location.

Instead of using the Time Machine Back Up, I wanted to start fresh, but just bring a couple of things over.  I brought over the Photo Library from my back up.

How exactly did you do that? You can not use TimeMachine backups directly - you must use the TimeMachine application to restore files from a TM backup - Use Time Machine to back up or restore your Mac - Apple Support  --  http://pondini.org/TM/FAQ.html

LN

That is what would be called "overhead"

A library's overall size is greater than the size of it's photo files simply added up together.

Thumbnails, edits, album data and may either things are in a library. The actual photo files are only one component.