Hi quocbinh2901
welcome to the Apple (user-to-user) Community!
Re: How to uninstall downloaded voices in Spoken Content (Accessibility)
Deleted files generally go to the bin, where they still take up space for whatever time is set in your settings --- often 30 days. You may just want to empty the bin, if there is nothing in there that you want to keep.
You may need to restart your Mac, (Apple menu > Restart) for the storage to show the updated amount.
Else: Community discussion thread with tips on removing downloaded voices:
Where do I go to delete additional Siri v… - Apple Community