I'm confused. Are you qualifying a welder or a welding procedure specification?
Table 9.9 lists the positions the WPS can be used for in production welds.
Table 9.10 lists the thickness range the procedure qualification supports.
If you go to the AWS website for errata, you will note that the heading for Table 9.10 should be corrected to include "plate". I think that may be the solution to your question.
However, a qualification using a wall thickness of 10 mm only qualifies the WPS up to 2T or 20 mm maximum.
Link -
http://www.aws.org/library/doclib/errata-D1.1-D1.1M-2015.pdfBest regards - Al