This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
Which of the following is not true regarding the second number of the instrument formula? 
Select and explain. 
A. Indicates the primary cutting edge angle, B. The angle is expressed as a percent of 360 degrees, C. This number is always 50 or less, D. It can be omitted to give 3 number code
C: This number is always 50 or less
Answer: C: This number is always 50 or less 
Explanation: The second number of a four-number code indicates the primary cutting edge angle, measured from a line parallel to the long axis of the instrument handle in clockwise centigrades.
The angle is expressed as a percent of 360 degrees (e.g., 85 = 85% x 360 degrees = 306 degrees).
The instrument is positioned, so that this number always exceeds 50.
If the edge is locally perpendicular to the blade, then this number is normally omitted, resulting in a three-number code.

Ref: Sturdevant's art and science of operative dentistry, 4th edition page 311