Does anyone know what does this mean?

Answer:
I believe the textbook is telling you which rounded version of pi () to use when solving questions regarding the geometry of circles. This is not a definite answer, as the question you asked is not completely clear cut. It is only my best attempt to interpret what your textbook means.
Answer:
Arc length
formula = s = rθ
s = arc length (in radians)
r = radius
θ = central angle in radians
Step-by-step explanation:
For a circle, the arc length formula is θ times the radius of a circle. The arc length formula in radians can be expressed as, arc length = θ × r, when θ is in radian. Arc Length = θ × (π/180) × r, where θ is in degree, where, L = Length of an Arc.
where X = 60,2 degree