Billing and Cost Management - Create Budget Unit issue

Based on the information provided, it appears you're encountering a display issue when creating a budget in AWS Billing and Cost Management.

When creating a budget, particularly when setting alert thresholds, you have the option to choose between "Absolute value" or "% of budgeted amount" for your threshold type. When you select the percentage option, the unit should indeed display as "%" rather than "USD" as you're seeing in your screenshot.

This appears to be a UI display issue. The system should be showing the correct unit (%) when you've selected a percentage-based threshold. Despite the incorrect display of "USD" instead of "%", the budget functionality should still work as expected based on the percentage value you've entered.

If you're creating a reservation budget, you would typically enter a utilization or coverage percentage threshold (such as 90% for utilization), and the system should recognize this as a percentage value even if the UI is displaying the wrong unit.

You might want to try refreshing your browser or using a different browser to see if the issue persists. If it continues, this would be appropriate to report to AWS Support as a UI bug.
Sources
Creating a reservation budget - AWS Cost Management
Creating a cost budget - AWS Cost Management