Need clarification about `system_time_offset` vs `last_offset`

The clock_error here is calculated via

```text
clock_error = |last_offset| + root_dispersion + (0.5 * root_delay).
```

Following the [chrony documentation](https://chrony-project.org/doc/3.3/chronyc.html#:~:text=chronyc%20is%20a%20command%2Dline%20interface,parameters%20whilst%20it%20is%20running.) "Last offset" is defined as "This is the estimated local offset on the last clock update.".

On the same page under "Root dispersion" we have the formula

```text
clock_error <= |system_time_offset| + root_dispersion + (0.5 * root_delay)
```

where `system_time_offset` is probably the value from `system time` you see when running `chronyc tracking`.

Which formula is correct?