Hello Karan
It means that the lead time for such quantity is too long and, in order to avoid a planned order starting in the past, system uses today as the start date, scheduling the planned order forward.
I suggest you to check the in-house production time defined on tab work scheduling or the times defined on the routing, if you are using detailed scheduling.
If it is OK for you to have a planned order starting in the past, then you can change the respective customizing on transaction OPPQ.
Regards
Caetano