It isn't multiplying the value by three. It's summing the value over every record in your found set--which is exactly what such a summary field is designed to do.
Define a field sCount, a summary field that counts your records.
Define a calculation field, cFractionTotal as
GetSummary (YourSubSummary'sSummaryFieldHere ; YourSubSummary'sSortedByFieldHere ) / GetSummary ( sCount ; YourSubSummary'sSortedByFieldHere)
Then set up a new summary field to sum cFractionTotal to get the value to put into your grand summary layout part.
Hi Phil, thanks for replying.
I tried your solution but it gives me the same figure as before in the trailing grand summary. Attached are a couple of screenshots showing what i've done with the fields created and how they show on the layout.
i figured it out. thanks