When I run antenna simulation,

I got the different VSWR results if the stop frequency setting is different.(Option1 0 to 3GHz & Option2 0 to 8GHz) 

Could you give the reasons for different results to me? and How do I get the same results? 

Here is Korea of south. Could I support this issue detail to Korea team of Simulia?

Thank you 

CST Studio Suite ​​​​​​​