Allow me to break down one part.
On that site in question, there is this statement:
In WWII Hitler's leadership convinced the Neutral German People to
kill 6,000,000 Jews,
kill 6,000,000 Christians,
and kill 7,000 Polish people.
So, according to that site, in the European Theatre of Operations, 12,007,000 persons died, apparently. That or Poles were neither Jews nor Christians.
Without even referencing other sites I know that many many more people died in that war.
The other possibility is that they are referring to the deaths at concentration camps. Again, from my knowledge of things, their numbers are WAY OFF. As in "too low".
The 7,000 Polish people (I think they mean "Poles") - What is up with that I have no idea.
My best advice to you: read it for yourself and make your own mind up. When they assert something, look at it critically. Are they actually saying anything, or do they say "we believe" *this* "to be the case".