about double unit

Dear Experts,

I have a question about double unit transaction.

For example,

1.  A material named: ABC , its base unit = KG,  and 10 BRD = 8 KG

2.  Do MB1B- 303, transfer material ABC from plant 1060 to plant 1050 with amount 0.8kg(= 1 BRD)

3.  After posting, the material document will show

303 -   1060   ABC   0.8KG  1BRD

303 +  1050   ABC   0.8KG  1BRD  (created by system automatically)

BUT sometimes  found the situation as follows:

303 -   1060   ABC   0.8KG  1BRD

303 +  1050   ABC   0.8KG  (empty)BRD  (created by system automatically)

We are so comfused for that situation and could not find the reason...

Please kindly offer me suggestions or solutions to solve this problem.

Thanks you a lot in advanced.

Ella