I just started with Profile Prism.  Instructions did not save what format to save the scanned image of the IT8 Target.  So initially i saved as TIFF, matching the format of the TIFF file used for the profile Target Print.  When followed the instructions to Profile the SCANNER, i had "60" "X's" and a warning message. The histogram had red on the leftside.  I did several scans with not much change.  Then i tried saving the IT8 Scanned image as jpg.  and the number of "X's" dropped to "4". 

Should i be using TIFF? Is there anything wrong with using JPG?

I have WF7620 Epson and printed the "...bright.tif" target file. Then used the IT8 Target and the printed file.  Followed instruction very carefully. then
Same happened when trying to Profile my Printer. Jpg worked but Tiff had around 50 X's.