If you look at MD04, the rescheduling date is based on the Stocks Requirement date.  

It does not take into account the parameters in Procurement and Scheduling in the Material Master.

In the net requirements calculation, the system checks whether warehouse stock or firmed receipts are available to cover requirements. If a material shortage exists, the system usually creates a new procurement proposal. 

The rescheduling check is used to change the dates of already existing firmed receipts not planned on the same day as the requirement to suit the requirement date. 

For this purpose, the system displays the appropriate exception messages with rescheduling proposals for these firmed receipts to be processed by the MRP controller.

You defined the rescheduling parameters in Customizing for MRP.

An important parameters is the rescheduling horizon period to be included.

1.  OPPQ per plant to Carry out overall maintenance of plant parameters.

2.  OPPR per MRP group to Carry out overall maintenance of MRP groups.

You can also define tolerance values for the creation of exception messages. 

These values define a time period in which no exception message is to be created, despite the fact that a rescheduling proposal may exist. 

The MRP controller can thus avoid a situation where too many exception messages are created if a certain buffer has already been planned for scheduling basis dates.

Rescheduling Exception Proposal

Bring process forward (reschedule in)

Within this rescheduling horizon, the net requirements calculation checks whether, after a requirement, a firmed receipt exists, which can be used to cover this requirement. Then the system displays a rescheduling date as well as the exception message Bring process forward for this receipt. The net requirements calculation then uses this receipt and the 
system will only create another procurement proposal if the receipt quantity is not sufficient to cover the complete requirement. Several firmed receipts can be used to cover one requirement.

The rescheduling horizon is always calculated from the MRP date. 

Postpone process (reschedule out), or cancel process

The net requirements calculation checks over the complete time axis whether availability could still be guaranteed without the receipt in question. If this is the case, the system checks whether the receipt planned here could be used to cover a future requirement. If the system can find such a requirement, it then displays a rescheduling date as well as the exception message Postpone process for this receipt. 

If the system finds no future requirement, for which the receipt is required, the system displays the exception message Cancel process.

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