Measurement points on control arm. What part are they referring to?

[abadsvt]

Hi guys. I have another question. So i got the measurements for the c5 corvette suspension. Now I am just trying to figure out exactly where these points reflect on the actual suspension parts. For example the UCA for the front suspension says the "Z" measurements are 9.75 apart from each other. I attached a picture to help explain my question. Red marks are the "Z" measurements. The "X" measurement in green. There stating that the X measurement is 19" out from center of vehicle. Is the green mark where they measure to? Sorry for all the questions. Unfortunately I don't know any suspension wizards in person to ask. Thanks

Josh