Clarify branch used by CCA when you assign an issue to Copilot (#57142)

Author: hubwriter

content/copilot/how-tos/use-copilot-agents/coding-agent/assign-copilot-to-an-issue.md

@@ -25,7 +25,7 @@ contentType: how-tos
 
 ## Introduction
 
-You can assign a {% data variables.product.github %} issue to {% data variables.product.prodname_copilot_short %}, just like you would with a human software developer. {% data variables.product.prodname_copilot_short %} will start working on the issue, raise a pull request and when it's finished working, request a review from you. For more information, see [AUTOTITLE](/copilot/concepts/about-copilot-coding-agent).
+You can assign a {% data variables.product.github %} issue to {% data variables.product.prodname_copilot_short %}, just like you would with a human software developer. {% data variables.product.prodname_copilot_short %} will start working on the issue, on a branch it creates from the default branch of the repository. It will create a pull request and, when it's finished working, it will request a review from you. For more information, see [AUTOTITLE](/copilot/concepts/about-copilot-coding-agent).
 
 If you haven't used {% data variables.product.prodname_copilot_short %} to work on an issue before, you can find some useful advice for getting good results in [AUTOTITLE](/copilot/tutorials/coding-agent/best-practices).