QTR-Quadtone RIP

Hello,

I have a question about linearization.  

The user guide and QTRGui help tell me to print the file 21step.tif, 
which linearizes using 21 different grey value measurements.

However, in the version of QuadtoneRip I have (2.4.2 for Windows), 
there are 55 spaces in the "Linearize" tab -- 5 rows of 11.

Furthermore, I have seen references to a 100-step wedge 
(100stepwedge.tif, found in the QuadtoneRIP program folder), and I 
have even heard somewhere about the ability to measure the 21-step 
wedge 4 times and input all 4 measurements, which the software 
averages for a more accurate read.

Which target should I print, and how should I enter the measurements 
into the 55 blanks I see?

I am a bit confused.

Thanks for your help!

Matt