Jno has almost certainly provided the correct answer.
If a thread is removed your answer obviously disappears with it, but that does not add to your count of 'removed posts'.
However this can often happen:
You compose your answer and click 'Submit'.
AB's 'incoming' server recognises your post but the 'outgoing' server is 'going slow', so the page you see fails to update.
Frustrated at nothing happening, you click 'Submit' again.
AB's 'incoming' server spots a duplicate post. It doesn't add it on to the thread but simply increases your score of 'removed posts' by one.
With a bit of luck, the 'outgoing' server finally updates the page, and you see your answer on the screen.
If not, you might be tempted to click 'Submit' again, resulting in your 'removed posts' score increasing yet again.
Chris