Don't create a transaction list with a top level. The calculations will need to sum for all items in the list even if only a single item is added
5.07-09a Check totals: If a check total of all transactions is needed, but again using the flat attributes modules is preferable
Related to Rule:
5.07-10 Add intermediate sub totals to transaction lists
Best Practice article:
Questions on this topic? See 5.07-09 Avoid using a Top Level for large lists of transaction data in our Planual forum.
Top Level Item and Parent Hierarchy