simulating Xin Ma, Guobin Wan, and Ning Ren paper in CST

I m simulating the Xin Ma, Guobin Wan, and Ning Ren paper which is related with FSS. Paper's title is Study on the Duality of Frequency Selective Surfaces with
Rectangular Complementary Elements. i am new in CST can you explain boundry settings. i don't know what i m doing wrong please help me.

best regards