How to apply self assess tax on Purchase Order for India GST?

Summary:

We have GST Tax setup and need steps on how to apply Self assess tax on Purchase Order , so same will flown in GRN and AP invoice through ERS.
When I am applying tax it is getting calculated as exclusive tax instead of self assess tax.

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):