Puzzled by values returned by the function depsoyd(Cost, Salvage, Life) from Financial Toolbox when Life is fractional

I am puzzled by the values returned by depsoyd(Cost, Salvage, Life) from Financial Toolbox when Life is fractional.

>> dep = depsoyd(13000,1000,2.5)

dep =

1.0e+03 *

6.857142857142857 4.114285714285714

Here the depreciation amounts do not sum to 13000 - 1000 = 12000 as I was expecting, summing instead 10971.42857142857. Would appreciate very much any clarification about how these depreciation values are been computed. Many thanks in avance!