Why are dots big and small in the PCA plot drawed with fviz_pca_ind()?

I use fviz_pca_ind() to draw a PCA plot, but the point size is different.

Why are dots big and small in the PCA plot which draw with fviz_pca_ind()?

I use the fviz_pca_ind() to draw a PCA plot, but the pointsize is deifferent.
this is my code: