Draytek Vigor2926L User Manual page 240

SMS sent. For example, 7 means the whole cycle is 7
days; 20 means the whole cycle is 20 days. When the time
is up, the router will reset the number of SMS sent
automatically.
Today is day XX in the cycle –Specify the day in the cycle

duration as the starting point which Vigor router will
reset the number of SMS sent. For example, 3 means the
third day of the duration cycle.
224 Vigor2926 Series User's Guide