Physical difference posted using movement type 701 and 702, But you can most difference in previous period, even you have allowed backdate posting in MMRV,
701- will increase the stock and 702- will decrease the stock. You also need to enable 701 and 702 for MIGO via configuration using T-code OMJJ or SPRO.
before making posting in 09- you have segregate your materials for negative posting and positive posting. Negative posting use 702 and positive posting 701.
Also make sure FI period is open for month 09 and MM period back date posting is allowed in MMRV. Then you manually process the inventory difference in MIGO. But you have enter the difference only in MIGO that will increase or decrease your stock in previous period.
It is not recommend approach, but I this will able to fulfill your requirement. You have look at this process accounting and valuation point of view.