Amend section about GPT-5.3-Codex (#60476)

Co-authored-by: Ben Ahmady <32935794+subatoi@users.noreply.github.com>

Author: mchammer01

content/copilot/concepts/fallback-and-lts-models.md

@@ -39,9 +39,10 @@ An LTS model is an AI model that {% data variables.product.github %} commits to
 
 ## Continuous access when premium requests are unavailable
 
-{% data variables.copilot.copilot_gpt_53_codex %} is available on paid plans with a 0x premium request multiplier, which means it does not consume premium requests. This ensures continuous access to {% data variables.product.prodname_copilot_short %} in situations such as:
-* Premium request quota exhausted: If a user has used their monthly premium request allowance, they can continue working with {% data variables.copilot.copilot_gpt_41 %} (the former base model) at no additional cost.
-* Overage controls disabled: If an organization or enterprise has disabled premium request overages and a user reaches their limit, {% data variables.copilot.copilot_gpt_53_codex %} will not remain available.
+{% data variables.copilot.copilot_gpt_53_codex %} is available on paid plans with a 1x premium request multiplier, which means it consumes premium requests. To ensure continuous access to {% data variables.product.prodname_copilot_short %} when premium requests are unavailable:
+
+* Premium request quota exhausted: If a user has used their monthly premium request allowance, {% data variables.product.prodname_copilot_short %} automatically falls back to {% data variables.copilot.copilot_gpt_41 %} (the former base model) at no additional cost to the user.
+* Overage controls disabled: If an organization or enterprise has disabled premium request overages and a user reaches their limit, {% data variables.product.prodname_copilot_short %} will fall back to {% data variables.copilot.copilot_gpt_41 %}.
 
 ## Further reading