shadow density for grayscale image

Hello. This is my first time to submit the question in this forum. I will submit the Black and white ad created in Photoshop to the magazine. The requiment is that for grayscale images, the shadow density should be no darker than 90% and highlights should be no lighter than 3%. I don't know how to check the percentage on the document I made. I checked HELP in Photoshop and website. But I couldn't
really get answer from them. I have little knowledge of printing. Please give me advice or helpful website. Thank you

Theyre telling you to do this because it keeps images from loosing detail in the shadows and highlights.

The way that I found to do this is by using Curves. Make sure your in grayscale mode, and open the curves adjustment under Image>Adjustments>Curves. Take the left bottom point on the line and drag it up until the Output reading is 3% and Input should remain at 0%. Then take the top right point on the line and drag it down until the Output reading is 90% and the Input should remain at 100%. That should do the trick for you!

Thank you so much, rooroo. I got it. http://forums.devshed.com/newreply.php?do=newreply&p=787225#