The "Hover Label" option provides a live feed of the measurements you are making. This is a great tool to reference the size of a line before / as you apply it to the plan. Enable Hover Label often used in conjunction with the dimension tool to make precise dimension lines.

Step 1: Begin a measurement or assembly.

Step 2: Go to "Options" and select "Enable Hover Label"

Step 3: Notice a box will appear that displays your measurements as you go.