I am using SHAP to get a further idea about my model features meaning. I have a XGBoost trained. it has retained 33 variables, however, when I use summary_plot or force_plot, it only gives me 20 variables in the graph. What is the reason for that? any configuration I can do to make it better performing?

Meanwhile, I double checked, by removing those variables not shown in the graph, my model performance drops dramatically. So those invisible variables are necessary for my model.