There is simple math behind the power of social distancing.
Generally, each COVID-19 patient can directly infect ~2.5 others. There are ~5 days between one infection and next, so each infected person can indirectly infect 244 others in a month. By practicing social distancing, one can reduce the transmission by half, so each person infects 1.25 others, leading to only 4 more cases in a month!