1) Please refer to the manual  Overview of Inventory Reservations and the scheme below to undertand the process of Reservation:

2) The DATE (or TIME) of Basis document in the chain of document should precede the dependent document. 

3) Reserve Creation Docuemnt should also be preceding Reserve Cancellation document. 

Reservations can be created by following documents: 

• Inventory Reserves (create reserve type of transaction)
• Invoice Received
• Goods Receipt Note

Reservations can be removed/cancelled by following documents: 

• Inventory Reserves (cancel reserve type of transaction)
• Invoice
• Goods Dispatch Note

If Reserve creation document date will be after Reserve Cancellation document

• Cancellation will not be performed, 
• Financial document can create the 2nd reserve. 

For example, if you create Goods Receipt Note and Invoice Received with current date and crete Invoice and Goods Dispatch Note backdated, in this case your reserves will be still showing in the reports and you can see double reserve on the same Customer Order or you can face with "Insufficient stock" error while posting Invoice or Goods Dispacth Note.