Hi Prabhat,
Hope you have got the answer for this issue already.
Please check your lot size method. Is it periodic or lot for lot.
Below checks may provide some clue for the orders generated in thousands.
1. Check the total period demand if the lot size setting is Periodic
2. Check if there is any calendar is assigned (receiving calendar at receiving location and shipping calendar at supplier location).
Kind regards,
Ravi Sankar Z