So, in a PI Datalink calculation, we have a PIAdvCalcDat('tag','start time', 'end time', 'time weighted') calculation; the time frame is a calendar month.
For the tag in question, the archive value from the last day of the previous month to the third of the calculation month is 'Calc Failed'.
During data validation, it looks like the Datalink calculation is interpolating from the last good value of the previous month to the first good value of the calculation month which is affected the calculation total.
We can modify the analytic generating the 'Calc Failed' to give a value of '0' instead.
The question is: am I right in my belief that the calculation is in fact interpolating?