Modifying the document by malechaneit · Pull Request #299 · javascript-tutorial/uk.javascript.info

ms - official international name for millisecond. 1 ms = 1 * 10**(-3) second (or 1e-3). Source : https://en.wikipedia.org/wiki/Metric_prefix .
0.000001 or 1e-6 - it's microsecond. Better name for this variable 'mcs' or 'us'. 'mcs' easier to understand.