When you build services, Liferay increments a counter in the service.properties file. This number is in both the service jar and in the service implementation.
It is a check between code with a service jar to ensure it is the same version as the one implemented in the service implementation.
When you get this message it means you are now out of sync - you have a newer service implementation than what the service jar you're using is or you have a newer service jar than the deployed implementation.
When working in a team setting, you have to manage the communication of the build number to all participants so the numbers remain equal. Often it is best practice to have one dev build services to keep this kind of thing from happening.
