Dimension Height

In the exercise for the dimensions it says the outer height should be 15 and the inner height should be 13… what is that referring to i cant figure it out…

In the dimensions manager you are setting the dimension height under the text tab.
If it is greyed out that means you are basing it on a text style which has a height set to it.
Either use a text style with no height or use one with the correct height.