Prorate Convention with Formula not calculating as expected

I am needing to calculate depreciation based on a short tax year, mid-qtr .  The Short Tax Year functionality in Oracle doesn't meet my needs as I am acquiring assets, but will be purchasing assets through the remainder of the tax year.  I have searched and been unsuccessful in finding any documentation to support this particular type of situation.  I have set up a new Prorate convention, entering the standard monthly ranges until I reached the point my short tax year range.  At this point, I listed the the date range that makes up each of my quarters and the midpoint.   I