Update Dependabot options reference for pull request limits

content/code-security/reference/supply-chain-security/dependabot-options-reference.md

@@ -542,13 +542,15 @@ Change the limit on the maximum number of pull requests for version updates open
 * If five pull requests with version updates are open, no further pull requests are raised until some of those open requests are merged or closed.
 
 > [!NOTE]
-> _Security update_ pull requests are not subject to this limit and do not count toward it. There is no limit on the number of open pull requests for security updates.
+> _Security update_ pull requests are subject to a separate, fixed limit of 10 open pull requests, which cannot be configured using `open-pull-requests-limit`.
 
 When `open-pull-requests-limit` is defined:
 
 * {% data variables.product.prodname_dependabot %} opens pull requests up to the defined integer value. A large value can be set to effectively remove the open pull request limit.
 * You can temporarily disable version updates for a package manager by setting this option to zero, see [Disabling {% data variables.product.prodname_dependabot_version_updates %}](/code-security/how-tos/secure-your-supply-chain/secure-your-dependencies/configure-version-updates#disabling-dependabot-version-updates).
 
+When either limit is reached, {% data variables.product.prodname_dependabot %} reports an error and stops opening additional pull requests until some of the open pull requests are merged or closed. For more information, see [AUTOTITLE](/code-security/reference/supply-chain-security/troubleshoot-dependabot/dependabot-errors#pull-request-limit-reached).
+
 ## `package-ecosystem` {% octicon "versions" aria-label="Version updates only" height="24" %}
 
 <!--Note: When making updates to this section, please make sure any changes are also reflected in `data/reusables/dependabot/supported-package-managers.md`.-->