Well, when I read watermarks I don't know why but I thought of those watermarks added to images :o)

I'll take a look in the robotplugin, or if you can elaborate more to explain to me (like I'm five yo) perhaps we can include it in the next release.

Thanks!!!

ok no problem...

Usually not all test will be passed. And with watermarks or also called thresholds you can define how many tests or how great the percentage of positive tests should be to have a somehow passed result. E.g. 5% out of your test are ok to be failed. Thats the unstable threshold.
The second one is the failed mark.

The robot framework plugin says:

Specify thresholds for marking a build unstable or passed. Thresholds are expressed in percentage of tests that passed compared to total amount of tests run. Builds with pass percentage under the blue threshold wild be marked unstable and pass percentage under yellow threshold will yield a failed build.