Then my friend.. you must understand that, that software doesn't even work without entering the locomotive type... and as far as the calculation is concerned... if one knows the right formula, both with/without locomotive can do the same result. The only thing that affects the final result is the incorrect data (length of carriages & locomotive) and I hope that the person who developed that software has already taken care if it.
If you believe there can still be some trial and error involved and you find out any growing discrepancy of opinion regarding the software, you can always contact the developer at this link only:
click here