Mostly correct. 
The actual height of the gridded portion of your tray is actually probably closer to 1.37" to 1.4" (there are some adjustments that have to be made for the plastic lip on the side), but other than that, you have the right idea.
There is an older tutorial here that explains what is going on with the measurements, and why it “used to be” very important to have the correct number in there.
I say “used to be important” because you don’t actually have to do that any more. As long as the top of the material is higher than 1.37", you can use the Set Focus tool and do it without a lot of measuring now. Once you have used Set Focus you will get a better view of the bed, and you can shift your design a little so that it falls onto the correct location.
It might help to understand that the image of the bed with the cutting board in it is the part that is distorted due to fisheye effect of the lid camera. You are trying to use the rulers at the top to measure the size of the cutting board, and it looks like the design is not coming in at the correct size, but the rulers pertain to the design overlay, not the picture of the material. What actually is “appearing” to be larger than 14 inches wide is the cutting board.
The Set Focus or Unknown Material height entry is what is used to correct for that effect in an algorithm, so that’s why it’s so important to have a good measurement there, and why it is important that the surface to be engraved falls into a range that the camera can focus on. Your first attempts were way out of range, and the algorithm was modifying the camera picture very incorrectly as a result.
That fisheye effect is lessened the closer you can get the material to directly under the camera, and it stretches the picture out at the edges of the bed.
So for the best design placement, what you want to do is center the design, and the material directly under the lid camera. Understand that the photo of the material is going to be a little bit stretched out at the edges, but the cutting board itself is still only 14" wide. And the rulers pertain to the size of the design, not the size of the cutting board. The size of your design is shown as 14 inches, so everything is looking good from a mechanical standpoint.
At some point long ago, Dan posted a picture of what they actually see from the lid camera, but I can’t find it now. It is an extremely bloated image. They modify that with the algorithm and send it back to our computers, so that what we see on our screens looks more like a normal picture. But it can still be a little stretched out at the edges.
So how can we be 100% sure of 100% accurate placement on something that spans a large area of the bed width-wise?
There is only one way that I know of, and most people don’t like it. But I will try to get the material and design as centered as possible, I’ll double mask the material at the edges, then I’ll run a light fast score of the outer rectangle at 10% power over the masking to see where it hits. If that’s acceptable, I go forward with the engrave. If not, then I shift the design by a hair and try the score again. It takes very little time, but saves a lot of material.
Okay, hope some part of that helped. It’s time for breakfast. 