Among the others, the draft describes the notion of accuracy and precision. In the following you can find the two relevant quotations, respectively from RFC 2330 and RFC 2679. It gives a lower bound on the clock's uncertainty.
Resolution is defined in terms of seconds.
However, resolution is relative to the clock's reported time and not to true time, so for example a resolution of 10 ms only means that the clock updates its notion of time in 0.01 second increments, not that this is the true amount of time between updates. If the clock reports a time Tc and the true time is Tt, then the clock's offset is Tc - Tt. For example, the clock on one host might be 5.4 msec ahead of the clock on a second host. For example, the clock on an old Unix host might tick only once every 10 msec, and thus have a resolution of only 10 msec. For example, the clock on a given host might gain 1.3 msec per hour and thus be 27.1 msec behind UTC at one time and only 25.8 msec an hour later.