I think there are well over 9000 patches of sampled color.
It is very accurate
Fred
The official total of patches is 9,261 on the target image that you print using your printer.
The IT-8 target I believe has 228 color patches.
There are stringent guidelines for these targets, so much so, that they get a CHARGE number, or build number.
Then color corrections are tweaked into a text file which Profile Prism accepts to match the target Charge number.
Now, the IT-8 is ready to use, and accurate.
The 9000 + color patches on the Printer target will produce a pattern that Profile Prism recognizes and which makes a Printer Profile to make your color as accurate as it can based on the color gamut of your printer.
*** Seriously, I make printer profiles for my HP Advanced Glossy. (Beautiful) But I don't have any HP profiles to compare...
On the other hand, one day Mike told me that he made a few profiles that were noticeably better than the commercial ones that ship / download with the Epson and Canon printers.
So I tried that on my Favorite paper; Epson Ultra Premium LUSTER!
Shazam! Side by side, mine was better.
So I did my Ilford Smooth Gloss. Again, the Profile Prism profile won.
I did my Ilford Pearl; same thing.
Not only are the results satisfying, but it's fun to learn and be able to "roll your own"
Fred