Extra Consumption while goods movement in production order

Hi Experts!

I am facing problem while confirmin production order through Co11n. i.e.while making goods movement consumption of Component increases by 1 qty.

suppose I have created order for A Material of 100 Nos. and this material A has BOM Component B=100 nos. and C=1.9 Kg. while goods movement system shows A = 100 Nos (101 Mvt) and B=101 Nos (261 mvt) and C=1.919 Kg , this is happening for several Material and Several Qty. only . Not or All Material and all the Time. can Any body explain why it is happening........

Thanx.

Dhananjay