pit volumes with two maps

Hi all!

I am from Hungary so my eanglish is not the best! Sorry

I have a problem..

I whant to calculate the fill of a pit. I have mayd two survays and maked 2 maps from them , one(upper) when the terrain was not touched, second(lower) time when they had taken out some humus and sand. I have the DTM menu  i have set up the two survays

 extrath-graphics     then build - triangles  then edit-trangles ( i have taken out the not good lines) then  analysis-volumes- tin to tin  i have strated with the upper to the lower. I have got a total cut and total fill m3 . But somebody teld me thay shoud be equal.. is this rigth? And how can that be rigth?

Becouse i got this total cut :16269,454m3     total fill:49430,395m3 

And what does this mean?  they have put  some sand on the first survay?

Thank you for the help folks!!!!!!!!!!

Oh and another.. I have a depo. I say it 180000m3  and another  landsurvayor told me it just 105000m3 and we whas working with the same survays... how can this happen? I have make a mistake somewhear? i will put this up to!

 I will put them on my download area here the two dwg-s if some whould be so kind to calculate it for me again to see what whoes the problem ..if there was a problem:)

Realy thans for the help