What amount of store occupy only files in a directory?

Hello I'm trying to do an exercise programming in bash where I have to get only the store of files in a directory but NOT all capacity of the directory.

I probe with: du -sh "$directory"*` but I get all the capacity and I probe with ls command but I couldnt.
Are there any way to get only files capacity of a directory?

Thank you so much!

Do you mean the exact size of the files as shown with ls -l ?

um no, I'm not sure, I think that I have to get the size only the files and not the size of a directory and subdirectorys.

could you understand me?