When you go to set your Level account you enter in your Income and Recurring Expenses then you are left with an amount left so you can decide what becomes your spendable and what will remain for you to save.
The Spendabubble is your spendable. It is the Income - Recurring Expenses, but not including your savings.
The Spendabubble amount will go down anytime you make a purchase that's categorized as general.
The Spendabubble will be filled by credits, incomes or transfers. In will only reset to full at the beginning of next month.