Formula (Percent) Average is Summerized a Few Points Off

In my summarized search, I have a column that does an average of profit per sale depending on whether all our numbers are in or not.

It looks like this:

Field: Formula (Percent)
Grouping: Average
The formula: CASE WHEN {custbody_origshipcost} IS NOT NULL THEN {custbody_origprofit}/nullif({amount},0) END
|| CASE WHEN {custbody_origshipcost} IS NULL THEN {custbody_profit}/nullif({amount},0) END

When viewing the search in detail, all the percents are correct. When viewing them in summery, they're a few points too high (like, should be 43.215%, is 46.121%)

There are 2 more fields that show me a sum of the amount and sum of the profit (it's also found on a transaction level). The percent field doesn't match the math done with these numbers.