Support Vectors SVM

I have read somewhere that the value of slack variables of support vectors is not 0. Does that mean the points lying in the wrong region e.g a positive point lying in the negative region will also be a support vector? I have attached one picture as well which shows that points lying in the wrong region are also support vectors. I am looking for an explanation of this phenomenon
It has 12 support vectors! the wrong point in the green region is also considered as one support vector!