Hi Ethan,
Please have a look at Re-initialization of the Material Stocks/Movements cube (0IC_C03) with 2LIS_03_BF, 2LIS_03_BX and 2LIS_03_UM in BW 7.x.
Reinitialization is not necessary if you did not enter any plants or company codes explicitly in the selection criteria.
Best regards,
Sander