Scratch

I think I see what's going wrong. The conditions used in your repeat loop are causing it to end too soon, and you forgot to change test by 1 in the loop, so maybe try using this instead:

when gf clicked
delete (all v) of [numbers v]
forever
 ask [What number would you like to test?] and wait
 set [numtset v] to (answer)
 set [reVal v] to [true]
 set [test v] to (2)
  if <(numtest) > (2)>
   repeat until <<((test) + (1)) = (numset)> or <(reVal) = [false]>>
    if <((numtest) mod (test)) = (0)>
     set [reVal v] to [false]
    end
   change [test v] by (1)
   end
  if <(reVal) = [false]>
   add (join (numtest) [is composite]) to [Numbers v]
  else
   add (join (numtest) [is prime]) to [Numbers v]
  end
 end