The "Default Wager Amount" setting in Odds Assist Pro controls the default amount setting in the "Total Wager" section of the Arbitrage Bets, Live Arbitrage Bets, and Low Hold Bets tools.
These tools show you how much you should bet on each side to maximize your earnings.
By default, the "Default Wager Amount" is set to $100, but you should update it to whatever you typically bet for arbs and low hold bets.
Whatever you put in the settings page, will carryover to these tools so you don't have to update them each time.