Sum 17
Sum 17 is read as outside advice worth following and a warning about a flawed plan.
Interpretation
The traditional meaning is a change of plans prompted by sound advice. Collections often add: if you were about to travel somewhere or sign something, it is better to postpone it.
The sum is not negative but corrective: it says your current plan rests on a false premise.
Probability
Three dice give 216 equally likely outcomes (6 × 6 × 6). A sum of 17 comes from 3 of them, or 1.4%.
For comparison: the most frequent sums, 10 and 11, come up 12.5% of the time, and the rarest, 3 and 18, 0.46% of the time.
The closer a sum is to the middle, the more often it comes up, and the traditional interpretations take this into account: the extreme sums have the sharpest meanings.
Advice
Listen to whoever disagrees with your plan, and put off your next irreversible step.