Can't exclude Bootcamp from Time Machine

Hello,

I just set up my external HDD today for use with Time Machine, thing is, I only have about 14GB of files on my Mac partition in my Macbook Pro, and about 53GB on a Bootcamp partition.

When Time Machine starts, it starts backing up a total of... guess what... 67GB.
Why the hell is it backing up the Bootcamp partition, and why can't I select it in the "items to be excluded" list? I'm really confused. It is greyed out.

I've tried searching around, and the answer I've been finding is mainly "Time Machine won't back up a Bootcamp partition".
Yeah ok, try telling that to my eyes and brain.

Cheers for any help!

L