Board Thread:Questions and Answers/@comment-216.74.198.38-20130416052333/@comment-3153244-20130416072026

Every time you hover over one of the "Send Bloon" boxes, there will be some info on it. For example, the very first box on the top row of bloons will the following information: Every time you click that box (or hotkey), your income increases by whatever the box says &mdash; in this case, $1, your income is increased. Let's say you clicked it once.
 * Grouped Red Bloons x8
 * Cost: $25
 * Income Increase: $1
 * Hotkey: 1

So every 5-6 seconds, i.e. whenever you receive your income, you will receive an extra dollar.