please explain use of set_output_delay

Hang on, I think I may be getting it. Is this correct?

set_output_delay specifies the minimum and maximum data arrival times wrt the clock.

so a maximum value is the value most ahead of the clock. +ve values before the clock and -ve values after the clock. This would explain my misunderstanding I think.

I'd be grateful if someone could confirm this or put me right...