The Storage tab frequently does not report correctly. Also check by choosing your Mac HD and "Get Info" (command-i). It may be different. Try rebuilding Spotlight index.
How to rebuild the Spotlight index on your Mac - Apple Support
Some of the space may also be from Time Machine Snapshots.
About Time Machine local snapshots - Apple Support
After you've freed up some space download Omni DiskSweeper:
https://www.omnigroup.com/more
DiskSweeper can give you a more accurate read of disk space than Finder or Storage Tab of About this Mac. Itcan also show you the precise size and location of all your files. It will inventory your disk starting from the files that take up the most space. If you want you can even delete files from OmniDisk Sweeper. But be careful some of the items may be important to your system.
Also, just running ODS should fix the storage number.
Check Mail menu > Window > Connection Doctor. If you have check marked “Log connection activity” turn it off.
For information about the Other category in the Storage display, please see Apple Support Topic
https://support.apple.com/en-us/HT202867
Also, empty the Trash if you haven't already done so. If you use iPhoto, empty its internal Trash first:
iPhoto ▹ Empty Trash
In Photos: File ▹ Show Recently Deleted ▹ Delete All
