Im not sure how to explain this but i'll try.

When I connect to ftp normally I just use my ftp hostname
mywebsite.com

Depending on the username and password I put it I am given access to different directories. If I login using a user/pass combo that only lets me access mywebsite.com/upload/users/ that user's home directory is upload/users/

But when I put in the full path ftp://mywebsite.com/upload/users/ and the login info for just upload/users/ it doesn't know what to do with it and gives me an error