total execution time as reported by auto_explain

Hi,

I was using auto_explain to log plans (with analyze option on) from
queries that take more than 500ms, something i found i little odd is
that the duration says 779ms but actual time says 269ms (almost 3
times lower), maybe some kind of instrumentation cleanup can explain
this?

2009-11-10 10:32:41 GMTLOG:  duration: 779.938 ms  plan:
    Sort  (cost=1943.99..1967.38 rows=9355 width=466) (actual
time=235.655..269.061 rows=4997 loops=1)

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Atentamente,
Jaime Casanova
Soporte y capacitación de PostgreSQL
Asesoría y desarrollo de sistemas
Guayaquil - Ecuador
Cel. +59387171157