Clarify Copilot Chat (dotcom) retention (#58352)

Co-authored-by: mc <42146119+mchammer01@users.noreply.github.com>

Author: ausdrew

content/copilot/how-tos/chat-with-copilot/chat-in-github.md

@@ -54,7 +54,7 @@ Depending on the question you ask, and your enterprise and organization settings
 1. To start a new conversation, click {% data reusables.copilot.pencil-paper-icon %} at the top left of the page.
 1. To see a list of your previous conversations, click {% octicon "sidebar-collapse" aria-label="Open sidebar" %} at the top left of the page.
 
-{% data variables.copilot.copilot_chat_short %} retains each conversation for up to 28 days from the last activity. After 28 days, the conversation is permanently deleted. You can view up to 100 previous conversations.
+{% data variables.copilot.copilot_chat_short %} stores up to 100 of your most recent conversations. Messages within each conversation are kept for 28 days before being permanently deleted. Once a conversation has no messages left, it's automatically removed from your history.
 
 ### Viewing and editing generated files within {% data variables.copilot.copilot_chat_short %}