Issue with GST display for different state

[tops9]

I have install Indian GST extension and configure as per user guide. But every time IGST apply. When buyer and seller are from same state then CGST and SGST should be apply. But in both case when seller and buyer are same state and different state, only IGST apply.
Can you please let me know why this happen. I am trying in fresh magento 2.1.6 installation.

Following is just for your information. My be it help to find out issue.
I have added Indian state, So on checkout page, Indian state comes in dropdown. But in admin GST setting i have added stated in textbox.

[sawbros]

Hello,

I am facing a similar situation. For sale within same state, CGST and SGST are applicable. This is displayed correctly on the front end as follows

However on the back end this displays as IGST on the order and invoice page.

I had also installed the Indian states same as tops9.

Your help in this matter will be appreciated.