The maxium amount of carbs one can have, is dependant on how they impact on the blood glucose levels...
Contray to what Hanna and IanD are saying you can have your carbs if you want them, but what you need to do is test to ensure what your are eating isn't causing your blood glucose to shoot up to unseptable levels...
If you know that you can eat lets says a meal/snack consisting 30-40g of carbs before you go training, and you find that your BG is fine and stable, if you don't train and burn this off, you might find that you have to decrease the amount of carbs to a lower level..
Testing is the only way to find out what is suitable for you..