Guilin Sun
Ansys Employee

I am not sure what problem do you want to fix? you can change the override region dimension and location, the same as a rectangle geometry. please refer  Ansys Insight: About override mesh in FDTD: its use and settings

https://optics.ansys.com/hc/en-us/articles/360034382634-Understanding-the-non-uniform-mesh-in-FDTD