Connie -
I am truly sorry I did not get to this earlier, I lost track of your post, and only stumbled upon it today.
I will start by addressing your expectations of the setup options you chose. Here is an image of an excel file I created to reconcile your numbers.
Your expectation is Dynamics GP would compute the correct periodic depreciation rates in column C with the data you provided it. It would only do so, if you plugged in acquisition dates, which represented half the periods of depreciation as well. Changing acquisition dates is not practical
Additionally, I think this approach is creative, but won't work, and if it would, 50% is not the number you would use, and since assets all have different original life numbers. The acquisition dates for the assets are not consistent. Here is an overview of what the depreciation should look like.
As you can see from the image above, the Life to Date depreciation (Depreciated So Far) is not consistent among this group of assets. The asset added in 1997 has been 79.5455% depreciated and the asset added in 2014 has been 27.7778% depreciated.
I have done what you are doing on numerous occasions. In my experience, the setup should be consistent with the typical configuration of every asset. The actual acquisition date, cost and original life should be used.
Then depreciation should be run to the current Depreciated to date of 2/28/2015.
Since the General Ledger posting has already been done, the General Ledger interface should be run and deleted instead of posted to the General Ledger.
One exception to this setup are assets which are retired/disposed of prior to the current depreciate to date. Retirements require a bit more finesse. If you are retiring assets, you should run depreciation on assets to the retirement date period and then retire them individually.
If you have additional questions, don't hesitate to ask, and/or reach out to me via email.