Safety not only means that your stats are way above average, it also means that you are willing to going to that school if it comes down to that.
Safeties also mean that you can afford them and it’s generally better if safeties have an auto-admissions policy that you are qualified for.
My safety is probably UC Merced. It has an auto-admissions policy that I qualify for, it’s relatively cheap for in state, and I would not mind going there if I get rejected from all my other schools.
You don’t want your safety to be a school that you hate (Ex: you think the school sucks, you hate the environment, the school culture etc.) as there is a (hopefully small) possibility that you will actually go there.