Journals for a Partial Retirement?

Hi all-

I'm looking for some guidance on the journals for a partial retirement. We have an asset with a cost of approx $69K. It was placed in service in Jan-20 with an 8 year life, STL depreciation method and mid-month pro-rate convention.

In Mar-20, we retired $30K. I know that in a partial retirement, Assets depreciates the portion of the asset that we didn't retire based on the method we use. But I'm still struggling to understand the second line below, where the Retirement Depreciation Reserve is debited $607.83.

In the cost history (below), I understand that JAN-20 shows half a month's depreciation, per the prorate convention. Feb-20 shows a full month's depreciation. But I just don't understand what's happening in Mar-20. Could somebody take a look and advise?