I have a basic upload form to upload mainly PDF files. If I upload a file at 87kb it only stores 630B on S3 for some reason like I'm missing something, but not sure as to what.
Actually it looks like you're using the ->put() method, not store.
I believe you're only storing the filename, and not the actual file, because you're trying to name the file a different name, which you can't do with put().
You need to use putFileAs or another one of the methods that allow you to specify the name of the saved file.