It means what it says - the issue types you are looking at are using different workflows or field configurations from the new ones.
Look at the project configuration screen and drill down into the "field configuration scheme" and "workflow scheme", you will probably find they say something like "for Bug, use field config/workflow A, and for the rest, default to B". Your existing issue type falls into "bug" there, and your new issue types will fall into "default"
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