[atlas] System tag

I noticed that the system tag “IPv4 stable 1d” is gone from my probe at: https://atlas.ripe.net/probes/1005104/ I use that tag as a criteria to select active orobes for measurements. But I noticed that my own probe was not included in my measurements. Which is weird since my probe has been online for 2.5 days (normally it is more stable, but my ISP had a small downtime). So my question is what triggers this tag? The tag is self explanatory but what does “stable” mean? Regards, Ernst J. Oud