below OnAgitEnd resets the value where he can get the prize again, if you remove all the sets inside that OnAgitEnd, it will only allow the guild master to get prize once only.
if you want it on certain date, you can modify and add the example below,
prontera,141,176,5 script Agit Reward#Agit1-1::Reward Giver 950,{
OnClock2100:
set $castle_claimed[0], 0; // everytime woe ends the variable resets
set $castle_claimed[1], 0;
set $castle_claimed[2], 0;
set $castle_claimed[3], 0;
set $castle_claimed[4], 0;
set $castle_claimed[5], 0;
set $castle_claimed[6], 0;
set $castle_claimed[7], 0;
set $castle_claimed[8], 0;
set $castle_claimed[9], 0;
set $castle_claimed[10], 0;
set $castle_claimed[11], 0;
set $castle_claimed[12], 0;
set $castle_claimed[13], 0;
set $castle_claimed[14], 0;
set $castle_claimed[15], 0;
set $castle_claimed[16], 0;
set $castle_claimed[17], 0;
set $castle_claimed[18], 0;
set $castle_claimed[19], 0;
set $castle_claimed[20], 0;
set $castle_claimed[21], 0;
set $castle_claimed[22], 0;
set $castle_claimed[23], 0;
set $castle_claimed[24], 0;
set $castle_claimed[25], 0;
set $castle_claimed[26], 0;
set $castle_claimed[27], 0;
set $castle_claimed[28], 0;
set $castle_claimed[29], 0;