Hi,  storywildstudios 

Move to the Transaction screen > checkmark the transaction > then from the top bar select Exclude ( same option is available by clicking the small triangle icon then checkmark Exclude this transaction (this is for duplicates, reimbursements, customer refunds, and returned purchases) )

OR to Delete the entire transactions delete the Bank/Credit card and add again to download last 90days transactions ( most banks allow only last 90 days transactions so check, PayPal allows to download transactions older than 90 days ) transactions older than the 90 days need to be uploaded manually.

Note: You can filter the transactions to display such Unreviewed, Transfer, Excluded etc.

Comment back for further clarifications.