This field follows the syntax of cron (with minor differences). Specifically, each line consists of 5 fields separated by TAB or whitespace:
MINUTE HOUR DOM MONTH DOW
MINUTE Minutes within the hour (0-59)
HOUR The hour of the day (0-23)
DOM The day of the month (1-31)
MONTH The month (1-12)
DOW The day of the week (0-7) where 0 and 7 are Sunday.

To specify multiple values for one field, the following operators are available. In the order of precedence,

Empty lines and lines that start with '#' will be ignored as comments.

In addition, '@yearly', '@annually', '@monthly', '@weekly', '@daily', '@midnight', and '@hourly' are supported.

Examples
# every minute
* * * * *
# every 5 mins past the hour 
5 * * * *