When you need to delete a group of orders on SelBuk under an specific date range, you may do it at the web version. That is at

Settings > Restore > Remove orders

Select the time range you need to delete. First year, month and day > Go

keep in mind: That process will create a backup, then remove from the cloud all orders older than the specified date and finally create a process to remove the same order on all devices on their next synchronization. 

The process will not affect the actual inventory on the products.