Exclude directories in Timeshift

**Edit: Ignore this question. Weird bugs happened today.** I am using Timeshift for full system backups. (all Home folders included). How can I exclude a sub folder of the home folder, like ~/Dropbox from the backup? I tried

+ /home/nils/**
+ /root/**
- /home/nils/Dropbox/***

and I tried **Edit: This is how to do it. I must have typed something wrong.**

- /home/nils/Dropbox/***
+ /home/nils/**
+ /root/**

In both cases, the Dropbox folder, including its contents, gets included in the backup, which I do not want.