Physiological Cross Section of a Muscle (PCSA)

This exercise is a visual demonstration of a cross section of a muscle. We are assuming the muscle is a circle. By entering different parameters of a muscle (e.g. mass, pennation angle etc.). This calculator can also act as a check for students to verify their calculations.
Which variables affect PCSA the most? Functionally, what does it mean for a muscle to have a larger cross section? What does it mean to find the physiological cross section?