Hello!
Please see your trigger attached. Use the constants to adjust the settings of your triggers.
For the trigger to work correctly, you will need to adjust the program option called "Market history depth". Go to Settings -> Monitoring Options, set "Default market history depth" to 30 mins. Be aware though that this might affect the amount of resources (RAM) the program will consume.
You will also need to start refreshing your markets at least at 31 mins before the off. If the conditions are satisfied, the bet will be placed no sooner than 30 mins after the market started refreshing (to measure the price drop over the last 30 mins).