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Since we're using the Banking page to bring your credit card transactions to your QuickBooks register, I'd recommend going to the Reviewed tab. Reviewing your January 1 to present transactions might be a great idea.
From there, you can compare your credit card statement to the ones that were added to your register. You can undo the transactions if necessary: Unmatch or move bank transactions after reviewing them.
After that, you can go to the credit card register, and compare the statement transactions again. You can click the Go to Register hyperlink in the Banking page. This is to ensure that there are no duplicates. In addition, doing this should also answer your second question.
Once you get to the bottom of this, you can already reconcile the account.
We'll be right here to guide you and keep everything aligned.