If they're in the shape of an exclamation mark, it's an indication that the blood dropped at an angle, and was splattered in the direction in which the dot in the exclamation mark is pointing. "Li Chang-yu further explains that when blood splatters in the shape of an exclamation mark, it means the person has been stabbed with a quick knife blow.
如果是驚嘆號，則表示是快速持刀殺人」，李昌鈺解釋。