How do I exclude a folder in Timeshift?

i have a folder /home/gravedigger/Graves with 9 subfolder that my other drives / partitions are mounted to. when i setup timeshift and run it it backs up the contents of the mounted folders just as if all that content is on the os drive when it isn't. how do i actually exclude /home/gravedigger/Graves/, or at least the contents in it's subfolders? thanks