A central angle is $\displaystyle 0 \le \theta \le 2\pi $. Now because $\displaystyle 2\pi \propto 6.283$ then 88.8 cannot be a radian measure. It must be in degrees, $\displaystyle 88.8^ \circ \propto 1.55rad$.

So if the radius is 10 the an arc of $\displaystyle 88.8^ \circ$ is about 15.5 units in length.

You must not confuse radians with degrees. All real mathematics uses radians; almost all calculators use radian measure as the default setting.