Jim is spot on!
You can use density as a guide to call your ink restrictions - there is no correct value as it will vary for each media you profile. You have to assess the ink restriction patch to see where the increase in density begins to tail off. After this point you are adding ink with no extra density & thus are wasting ink. Use your eyes to see when the patches stop getting darker. Better still use a densitometer to read the changes in density - when the increases get smaller & smaller to a point where they are around .05 you might as well call the restriction at this point. Some media bleed at the top end so that makes your call easier - stop before it bleeds.
A better way of deciding on your ink restrictions is to use Chroma rather than density. This will tell you when Cyan has reached the maximum cyan that can be laid down on the media - which is what we are looking for. If you use density as your guide, you can often push the Cyan into blue before calling your ink restrictions as all you read is density rather than color.
The good news is that Onyx 7.1 will be available in September (free upgrade from current v7) and this will have a “measure tool” which will enable you to assess chroma as well as density with your spectro device.
By the way - why use Profile Maker to build Icc profiles? If you have Production House v7 you have everything you need to do the entire job - it is all built-in and the new Onyx color engine is superior to the logo engine provided by Gretag Macbeth - especially in the shadow areas.