When trying to transfer by content items you will only have the choice of moving them to the section/categories that are already set-up up on the destination site.
If you want to move the data by sections or categories it will grab everything in that section or category and create a new section/category on the destination site.
Note if you have sections or categories with the same names you will get an error.
To fix this use "edit" and rename the section or category to something else.
