Usage in Devin counts toward the Codex and ChatGPT Work usage already included in your plan. You can let Devin use all of it, or set a lower limit for Devin in your settings.
OpenAI models are part of the model mix Devin Cloud uses in Lite, Normal, Ultra, and Fusion modes. Once you connect your ChatGPT account, your plan pays for the OpenAI-model share of each session while other models draw down from your included Devin quota.
By combining Astra on your ChatGPT plan with SWE-2 on your Devin plan, your quota can go further than ever before.