When you have enabled (checked on) the "Bet Maximum" feature, it means that the bet slip automatically enters the maximum stake amount for you on each of your wagers.
If you do not wish to use this feature, please make use of the check box next to the "Bet Maximum" to turn it off.
When you have disabled (checked off) the "Bet Maximum" feature, it means that the bet slip no longer enters the maximum stake amount for you on each of your wagers.