Google is very clever at working out what is what, the URL is only 1 of at least 200 factors, I wouldn't be overly worried just get it about right.
To the best of my knowledge the URL factor works on a sliding scale i.e. the nearer the beginning a word in a URL the more weight it tends to have over other words in the URL.
Having said all that I would guess even if you got it exactly right and assuming Google only uses 200 ranking factors you would have completed 0.5% of the ranking structure. Sorry if that makes sense??
But it's definitely worth making sure you get it as right as possible, consider the following...
- URL length
- Most important keywords as near the beginning as possible
- Avoid using abbreviations, Google may not interpret them properly
And finally remember that Google bot is trying to work as much like a human as possible, so if it looks commonsense to human then the chances are that Google sooner or later will adopt the same principle.
All the best and good luck