What you said is correct; the only problem is that with the numbers you quoted, the total probability of rolling a number in the range [0,10) is 2/16 + 1/16 = 3/16 < 1 :) The numbers you meant to quote, as borne out by your data above, are a 10/16 = 5/8 chance to get a number in the range [0,5), and a 6/16 = 3/8 chance to get a number in the range [6,10). (Equivalently, a 12/16 = 3/4 chance to get a number in the range [0,5] and a 4/16 = 1/4 chance to get a number in the range [6,9], but since that doesn't partition the [0,10) range evenly, it's less instructive.)
