Variable size item problem in BOM

hi all,

We have semi-finished material with componets as variable size items (item cat. R)

Now in the variable size tem data, Size 1 = 1,406 MM, Size 2 = 1,220 MM. Numner is 1 ST, formaula place is blank.

Qty Var-Sz Item is calculated by system is 3.957 M2. On what basis this value is calculated?

In the component material we have maintained a componenet scrap quantity as 15%.

BOM ratio of header : component = 1NOS : 1 ST

Again when we create a production order for the header, for 1 NOS header quantity component qty becomes 2.

For 2 NOS of header qty, component becomes 3 like this.

Why this happens..

Regards,

Srijit.