You may see items flagged for warnings or errors on your dataitems page where the editor shows different counts or no errors or warnings at all.
Warnings/Errors about things that are not wrong:
This sometimes occurs with items moved from the old editor into the new and not yet edited in the new version, or items that were edited before updated validation rules were published.
This is a known bug, and the errors and warnings shown in the editor are correct; the DataItems page can fall behind but can be refreshed by simply editing the falsely-flagged field in one of the dataitems, and then saving the item in the new editor. This will trigger validation of all items using current rules.
Warnings/Errors from DataItem context
Errors and warnings shown on the data items page show problems that can have a larger scope than the single item shown in the editor. For example, you may have an Article/BlogPosting that includes the Publisher, and the error or warning shown on the dataitems display may mention the publisher logo sizes; the editor only shows the properties of the Article, which has a publisher, but in the context of an Article, Google may have rules that apply to the publisher logo that are not applied in the case of any Organization -- the notice will appear on the DataItems page because the context of how the Organization known. Clicking on the error or warning button on the dataitems page should explain where the problem occurs, although even the edit page for that item may be missing this context and so show no errors or warnings. The edit page for the logo itself, however, will show the recommended fields for height and width, shown as only recommended because it is only the context of the Article that requires these.