I’m having the same problem too.
It looks like the import process re-creates the category list rather than actually importing the data. If there are two categories with the same name they are interpreted as a single category and the posts are consolidated.
Perhaps there is a work-around or else each category needs a unique name.
After a lot of trial and error and the lead from esmi above, I found that I could center a table with this as the beginning of the table code:
<table style=”width: 480px; margin: 1px auto;” align=”center”>
(The key was the “margin: auto” setting. In my case I also wanted a 1px margin.)
Hope this helps others.