Guillermo, because in your options list, you have numerical values under the "name" column, the values of your variables are actually numbers rather than strings (which are represented as '16', while numbers are represented simply as 16).
Anyways, I have attached a version of your form that has the right behavior for the second question, I believe. Do have a look at both the constraint and the relevant column, as I changed both for p6.1 and p6.2
Hope this helps more.