Production order forward scheduling scheduling margin key

Hello,

I try to schedule manually a production order. I use a scheduling magin key with 1 day in margin before production and 1 day in margin after production.

When, i do manually a production order (not created by conversion planned order/production order), I fill a scheduling margin key and a scheduling type (forward) and a basic start date.

I push button scheduling and automatically the scheduled start date is equal to basic stard date + 1 day. I understand this result because the system add the margin key before production. But If I do the same with a big quantity in production order, the difference between scheduled start date and basic start date is equal to 2 days.

When I try to schedule in CA02, the result of schedulinf modify the basic stard date in the result log. So with a big quantity, the difference between schedule start date ans basic start date is equal to one day.

I do not think that the customizing in OPU3 can influence a manually scheduling in a production order.

Have you an idea please?

Thanks fo your return