Special Rules - Observation Advantage

Hi,

Core game - scenario 3 - special rules : "The side with the Observation Advantage first targeting die does not cost an HQ. However, the maximum number of targeting dice rolled still remains the same."

If you have the Observation Advantage, you may fire with your reserve artillery with no cost (no HQ spent), OK.

But, does it mean that your opponent may fire FIRST with his Reserve Artillery if he has the Observation Advantage during your turn ?

"The side with the Observation Advantage first targeting die does not cost an HQ. However, the maximum number of targeting dice rolled still remains the same."

this means that if you have Reserve Artillery 4 and order it, you can use up to 4 targeting dice (die 1-6), and instead of paying 1HQ per die, you pay 1HQ less
so
4d = 3HQ
3d = 2HQ
2d = 1HQ
1d = 0HQ

so if you roll only 1 targeting dice (meaning no hit can be on target), you pay no HQ

your opponent's artillery can NEVER fire in your turn.

Thank you !