Your TALK Mastercard is a prepaid debit card, which means the spending limit is basically the amount that is loaded into the card. However, you can control how much is loaded into the card and when.
To set card limits open the card view of the desired card. Under Spending Limit enter the spending limit amount and the frequency and click the Save Button. Once the limit is set, the card won't be able to be loaded a total amount greater than the limit amount entered during the period of time selected. Daily periods begin everyday at 12:00 AM PT, Weekly periods begin every Monday at 12:00 AM PT and monthly periods begin on the first of the month at 12:00 AM PT.
In addition to setting limits, you can chose to autoload the card on the period of time selected. See the Autoloading cards article for more details.