asset a/c

hi sap gurus,

when ever u have to sale of asset in f-92 the system automatically generated 6 linte items, in that entry

01 CUSTOMER A/C................DR

70 ACCEU DEP A/C...............DR

40 ASSET SALE A/C..............DR (C)

50 TO ASSET SALE A/C (C)

75 TO ASSET ACCOUNT

50 TO PROFIT ON SALE OF A/C

here contra entry appears. what is the reason. pl explain

with regards

raj