Drop Shadow renders differently when i export to PDF?

So I have a drop shadow on a text box in InDesign. When I am working, it looks like this:

When I export to pdf, it looks like this:

Obviously, the simplest fix is to just use a black rectangle and place it in the position I want it to be in, but I want to know why this is acting like this and how to make it stop.

These are my drop shadow settings, if that helps: