Different results for the same action in MI10

hi gurus!

im new in this module and im having an issue with MI10 transaction, there are some materials where the difference get posted, but others where the total ammount gets postes.

for example:

Material 005 has -100 units

Material 006 has -100 units

if i use MI10 to post 10 units each i get as a result:

Material 005 has 10 units

Material 006 has -90 units.

why do i get this difference?

Regards!!!