This happens because of your "add/delete" keywords activity.
Whenever you delete a set of Keywords and re-add them the following days and re-delete them, re-add them, the update date stays on the last time that you have initially added those Keywords.
We highly recommend that after you re-add a set of Keywords, please make sure to manually update them by clicking the Update Keywords Rankings and wait for the update to complete and this will resolve and give the updated Keywords.
We hope you find this helpful! If you need any further assistance, please contact us and we'll be more than glad to help you out.
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