He doesn't "think she invented estate tax", no. He thinks she tries to mislead by only mentioning 500 million plus households as those affected (which wouldn't affect him) and then adding "going back to 2009 rates" - which means tax on 5 million plus estates, affecting him directly.
Btw, is 5 million+ estates count as 4 out of 1000? Or 500 million+ ? I would assume the latter, which means this figure is also misleading voters.