Generally, the clock will get stepped forward or back when the time offset is greater than the "step threshold" which by default is 128 milliseconds. But NTP also has spike filter, so the "step threshold" must be exceeded for more than the "stepout threshold" which by default is 300 seconds. In other words, even when there a few spikes within the "stepout threshold", those updates can be ignored and the clock will continue to run slewed.
The interval for queries to NTP time sources is the "poll interval". The default is 64 seconds, but NTP will automatically increase this up to 1024 seconds if computed time errors from the upstream NTP sources do not increase.
