Hi Vinod,
System is allowing you to post higher amounts during premature settlement because you are using "New basis" for changing rates and dates during netting.
The logic is when you tick "New basis", system allows you to change netting, hence there is no standard or fixed amount that is been picked up.
Please deactivate " New basis" and try to post a higher amount during rollover/ premature settlement, system will throw the required error (T7104).
Regards,
Manish