Conversion of bags to tons

Hi

I have an issue of a conversion of 25kg bags to tons which I'm thinking could be a bug

I've done 2 separate sales orders of a 100 25kg bags the product in each case was the same. The supplier needs the purchase order to be tons

The first sales order was used to create a normal purchase order and the 100 bags was converted correctly into 1.5 tons

The second sales order was used to create a direct delivery purchase order but the 100 bags did not convert to tons it stayed as a 100 bags the costs totals were the same

Has anyone else come across this or is it a bug?