When this option is checked, and this project is configured to use a Source Code Management system, then Jenkins will try multiple times to check out from the specified SCM system until it succeeds.

The default behaviour, or if this value is set to `0` is to mark a build as failed immediately if checking out from the SCM system fails.

Setting this to a higher number means Jenkins will attempt to check out from the SCM system that many times, with a ten-second delay between retries.
If the final attempt also fails, then the build will be marked as failed, and execution will stop.

As plugins can contribute different Source Code Management implementations, it's up to each individual implementation to define what constitutes a checkout failure.

If this option is not checked, then the system-wide default value from the Configure System screen will be used.