You're putting them in the correct place.
Those are not the correct sizes.
It's 48, 96 and 192.
S and L sizes currently seem to be 1000.
It doesn't take a while to update, it's just your browser will cache the last copy of the image for performance reasons. On Windows you can do Ctrl + F5 which should trigger a hard refresh, or Mac you can do Cmd + Shift + R.