[check_postgres] threshold measurement unit for --action=hot_standby_delay

[karfunckel-checkpostgres at yahoo.de]

Hallo, 
can anyone explain me the meaning of the values in --warning/--critical when using it with --action=hot_standby_delay? What is the "measurement unit"? Are the results in seconds, MB, ...?

In the Documentation I only could find "The valid options for this option depends on the action used" and "...the delta between xlog...".
The knowing of the "measurement unit" is important for the decision what values should be used for the threshold. 

Example: The lag of 1 second oder 1 file differenz would be more than ok for me, but the lag of 1 minute would be not ok.

And the results I receive are so different that I dont kwon how to interpret them:
First result: time=0.01 replay_delay=86040;10;20 receive_delay=74800;10;20
a second later: time=0.01 replay_delay=0;10;20 receive_delay=0;10;20

Thank you for your help,

Karfunckel