Leonardo refactored the billing page for the koyeb/control-panel repository, focusing on accurate display of database storage usage and associated costs. He introduced new React components and TypeScript enums to standardize units for usage and pricing, ensuring clarity and consistency across both desktop and mobile views. By differentiating database storage metrics from other usage types and adopting immutable variables for isDatabaseDataUsage, Leonardo improved billing accuracy and reduced user confusion. His work emphasized maintainability and cross-platform consistency, leveraging front end development skills in JavaScript and TypeScript. Over the month, he delivered one feature with targeted code quality improvements and no reported bugs.