Not currently (and it can't be done via a template edit or you will screw things up). The Min and Max amounts are determined programatically via the Bet Entity. Right now the Min is hard coded to 1, however, in the future, the Min will be determined by evaluating both the default and available cash (which ever is LOWEST would be the value passed to the spinbox.. eg. if the default was set to $500 and the viewing user only had $100, the min would be $100 where as if the viewing user had $1000, the min would be $500.
I'll move this to suggestions since its already planned.
Phase I of this has been implemented (Phase II will come with SB 2.1)
I've added a new option that allows you to set a default value for the Wager amount.
Note: There are several conditions that will effect the final default value. For example, if you set the default value to 100 and the viewing user only has $50 available cash, the default will have a final value of 50 when rendering the form.
And as you can see, the default amount is now 100 instead of 1.
Note: I've added the Min and Max wager amounts and removed the Available Sportsbook cash (as the Max Wager Amount IS the Available Sportsbook cash IF its less than the Max Wager Amount Setting (which will be part of Phase II).