This is what you need after you've done the set stuff and get what's going on with subtraction...  If you still need to "count down" or count on your fingers to get the answer, then this is how to fix that!

First, you need to get a yardstick.  (If you don't have one, most hardware stores will give you one for free.)

Next, you need to get a game piece or a rock -- just something you can use to mark your place on the yardstick.

Check it out:

Start by putting your game piece on the 10...

Now, move down 6 places (since it's -6)...  Just like you'd do on a board game if you got a penalty and had to go back 6:

We land on the 4...