You can ignore any transaction by tapping on it and taping the "Ignore" row.  There are two options:
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Ignore from Budgets - This will keep the transaction in your spending report but will ignore it from your budgeted spending.  This is useful when you have a large ticket item you have saved up for (like purchasing a car or vacation).  In such a case, you often don't want it to blow out your monthly budget, but still want to track the fact that you spent that money.

Ignore from Everything - This will ignore the transaction from all budget, spending and other reports.  The transaction will still show up in your Transactions tab.