What is the 16 on a Tape measure mean?

What is the 16 on a Tape measure mean?

The 16 is red and other numbers are black, and the 16 has arrows facing outward

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Getting the middle of the stud on the line I would think is hard unless the middle is marked. I honestly rather prefer marking by the side of the side
What is the 16 on a Tape measure mean?
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