What is the mining of #define SHUT_DOWN_TIME_OUT 20000UL?

Hello

I'm using the "en.fp-sns-allmems2", which send data from sensor with a ultra-low power consumption. I'm traying to increase the time in which the sensor is in shut down mode.

I think that I've to change the value of the variable  SHUT_DOWN_TIME_OUT which is define in code like this

#define SHUT_DOWN_TIME_OUT 20000UL"

¿Can anyboday tell me how is translate to seconds 20000UL?

Thanks