Typically, the volatility of the crypto currency is calculated within a specific period, as in the example above. The period can be any - week, month, year. But for a period of less than a month, few expect it, because during, say, a week the rate can only grow or fall. On the basis of monthly volatility, one can already draw conclusions, but more often volatility is taken for forecasting or trading strategies in a few months or a year.