Figure 1. 1PPS Example
In the above example the initial observed 1PPS offset is -3400. This value is doubled and applied to sfptpd using the ptp_rx_latency parameter as 6800.
sfptpd is restarted and the next observed 1PPS offset is -300, this value again is doubled and applied to the original compensation value (6800 + 600 = 7400).
sfptpd is restarted and the final observed 1PPS offset is +50 meaning the previous compensation value caused sfptpd to over-compensate, so the +50 is doubled and subtracted from the previous compensation value (7400 - 100 = 7300).