Formula help!

Hi All, 

Trying to figure out a fix to one of my spreadsheets at work.

Issue: I need to find a way to filter out entries of data from a dropdown specifically for a certain set of cells. 

Any patient that is designated under GM team needs to be removed from a overall summary on another page. See below: 

I would like to visibly show how many patients are being deducted from 'Mark' that are under GM team. In the above example the overall figure for GM should be 55, with the 5 being removed from Mark. However at the moment it is 60. 

Any help would be greatly appreciated.