Finishes: Colors & Stains

The phrase I/ I'll bet you do,  means I really believe you, so much that I'm willing to make a bet on it. 

phrase. You use expressions such as 'I bet', 'I'll bet', and 'you can bet' to indicate that you are sure something is true. [informal] I bet you were good at games when you were at school. I bet you anything you like he's a pimp.