The ratio of earned value (EV) to actual cost (AC), also known as the cost performance index (CPI), is a measure used in earned value management (EVM) to assess the cost efficiency of a project's budget. A CPI less than 1 indicates that the project is over budget, meaning it is costing more to complete the work than was originally planned. In this case, a CPI of 0.9024 suggests that for every unit of currency spent, the project is only earning 0.9024 units of value, thus earning less value than was planned. This is a critical metric in EVM as it helps project managers understand cost performance and forecast future cost performance issues.
References: PMBOKGuide - Sixth Edition; Professional in Business Analysis (PBA) Reference Materials.