The Reserved Amount setting allows you to set the amount of investment capital that you want to reserve inside of your exchange. This can be useful to ensure you have capital available to invest after a flash crash. This amount will remain when all of your capital may be invested by your open Traders. This setting can be found in your "Exchanges" area. You can edit the setting of a live exchange by pressing the "edit" icon.
Note: This is also a great way to take profits. If Wealthybot has invested all of your capital you can set a number here that Wealthybot will "reserve" over time and then you can remove these profits once they have accumulated.
You can then check the box and set the field as you wish. This amount is in Tether since that is what Wealthybot is using to Trade with.