What does the speed of regulation mean?
The speed of an induction motor depends on the mechanical load. The speed regulation of a motor expresses how much its speed varies between no-load and full load. The speed regulation is expressed in percent of full load speed.

Consider a 2-pole 50Hz motor with synchronous speed 3,000 RPM, no-load speed 2,950 RPM, and full-load speed 2,750 RPM.

$$
SR (\%)= \frac{\omega_{\textrm{no-load}}-\omega_{\textrm{full load}}}{\omega_{\textrm{full load}}} = \frac{2950-2750}{2750} = \frac{200}{2750} = 7.2 \%
$$

Further reading: http://www.most.gov.mm/techuni/media/EP02043_2.pdf