Hi
Looks like the max_liab constant stops the trigger from betting if the maximum liability on the lay bets is greater than max_liab.
If you want to limit the bet size to 50.00, in the Dutching trigger try changing the expression in the Amount to win field
from: current_bet
to: IF(current_bet > 50.00, am_to_win, current_bet)
please test in test mode.