Hi Marcos,
The results in the API will only reflect the results shown in the Google Ads UI. You may refer to this
guide for more details. Setting the
dailyBudget in your campaignEstimateRequest should work as expected. If the results do not match with the UI, kindly let me know by providing a screenshot of the UI and the SOAP logs in the API so I can further check. However, if you think the results are not what you are expecting, you can open your concern to the AdWords Community Forum as the product owners are better to provide insights to your concerns.