Sitoo,
You have evidently created your rescheduling horizon to behave in this way. If you want the system to create schedule lines earlier, then you should reduce the the duration of the rescheduling horizon. OMDW.
I also suspect that the planned delivery time in your scheduling agreement does not match reality. It probably should be longer, considering that you have a PO with a date in May.
Best Regards,
DB49