See https://docs.sonarqube.org/display/SONAR/Documentation for current functionality
The leak period and two other periods can be configured globally and will be available and common to all projects. Go to Administration > General Settings > General > Differential Views to set these properties.
The leak period can be overridden at the project level, and two additional periods may also be configured specifically for the current project. Select your project and go to Administration > General > Differential Views to set these properties.