Sometimes, we do end up with duplicate transactions due to issues on the bank side or the way we fetch data for transactions that change date and/or descriptions within your bank's website.  We're confident that we can detect these duplicates better as we improve our algorithms.  In the meantime, you can manually exclude these duplicates. Here's how:
 
1. Click on the Transactions tab. 
2. Find the duplicate transaction in the table, then click the tiny triangle on the right side of the row.
3. In the expanded detail select the checkbox to Exclude this transaction
4. Save
 
Note: Multiple transactions can be excluded at once.

In the table, check the box to the left of each transaction that you want to exclude.
At the top of the table (and below the graph), click Exclude.