What is the meaning of 7x in a score 366-7x?
For some disciplines (e.g. ISFF 10m Air Pistol) the target has an additional ring within the 10 ring which is scored as 'Inner 10'. It is still scored with 10 points but during a competition the number of inner tens is used to break a tie. The 'inner ten' is represented as '10*' or 'X' or '10.1'. A score '366-7x' is '366 points with 7 inner tens'.
Also in some rifle disciplines, where the target has an inner dot, the 'Inner 10' is awarded when you not just touch but completely shot off the dot.