Issue:
You notice that the sqlservr.exe process is using more memory than is configured in the Maximum server memory (in MB) option.
Cause:
The Maximum and Minimum server memory options apply to the SQL Buffer Pool only, and not to other aspects of the SQL Server process. The SQL Server process will acquire more memory than specified by max server memory option because both internal and external components can allocate memory outside of the buffer pool.
Solution:
When planning your max server memory take into account that addition memory will be required by the sqlservr.exe beyond the SQL buffer pool. In general plan for an extra 1-2GB of memory for other functions of the sqlservr.exe process, and reduce the max server memory setting by that amount.
Thus is you would like the sqlservr.exe process to use no more than 8GB RAM configure max server memory to be 6GB (6144 MB).