If I understand clearly, you just need to calculate the no.of Recons yet to make up for 85% of the metric.
If that is so,
CEILING([YTD Total Recons] * 0.85 - [YTD Within 30])
This gives you the minimum no.of Recons necessary to reach your goal %.
This could also be completely wrong if my understanding was different from your question.
Hope this helps.
I am getting an error with this calculation.
Not sure why as I only have one data source and the fields are calculated totals.
But to clarify more, the above chart shows 80.8%.
In order to hit 85%, the totals would have to be 57 recons within 30 out of 67 total. These numbers would make it 85.1%. That is saying that if 15 recons were completed at 100% for the rest of the year, the 85% would be made. If one doesn't make the 100% metric, than the number increases.
I guess my thinking is along the lines of ( [YTD Within 30] + 1 / [YTD Total Recons] + 1 ) where the +1 would continue until the division equaled 85%