This is called de-lamination. It is caused by dust and dirt particles that get trapped between the layers of glass when they are forming the window. Over the years these breakdown and leave the deformations that you see. I doubt they will spread inward but they will go around the window on the edges. This is pretty typically of aftermarket windshields unfortunately.
Let me know if you have questions. Thanks
Tuesday, November 5th, 2019 AT 7:30 PM