Replenisment control behaviour

Hello,

I try to understand replenishment control behaviour in the system:

I've made all necessary customizing settings:

- Storage type for replenishment

- movement type for replenishment and assigned it to storage type

- Activated storage type search

- Extended material master on storage type and added max. bin quantity, min. bin quantity and replenishment qty.

Everything works fine for t-code LP21- but i can't understand on thing:

1st case:

In material master i enter:

Max. qty - 74 pc

Min qty - 1 pc

Replen. qty - 50 pc

In LP21 system defined requested qty as 50 pc

2nd case:

In material master i enter:

Max. qty - 75 pc

Min qty - 1 pc

Replen. qty - 50 pc

In LP21 system defined requested qty as 100 pc

What is the logic? why requested quantity changes from 50 to 100? Doesn't have to be alsways 50 pc?

Thank you in advance - for helpful or correct answers will be points.