Double-counting only applies when your major has more than 180 degree-applicable units (the double-counting policy is here).  The minor units are not considered for double-counting eligibility.  That said, some of the extra units you took as part of your data science minor can be directly applied as advisor approved electives in the MS portion of your BMS degree.  Specifically you can use:

• Up to 4 units of DATA 401
• Up to 7 units of DATA 401/402/403
• Up to 1 unit of STAT 419 or DATA 451 (depending on catalog) as needed to reach an even multiple of 4 units.

If you are a MS student with a BS in Statistics with the Data Science minor please discuss your options with the CSSE graduate coordinator.