The available column shows you what you can carry on that backplane, the non-blocking shows what you would need in the worst possible scenario. Remeber the software assumes full theoretical load to calculate the non-blocking value. Again, count up what you really have and subtract the available number. That's your real over-subscribing value.

FYI - If you had more station cards than trunk cards I wouldn't worry too much as it's impossible to queue calls without available trunks. If you have more trunks, then you would have a place to load up on calls and possibly approach blocking. Of course this is predicated on the the assumption you handle primarily inbound calls. Just don't forget you have two places for potential blocking: within each cabinet and on the ATM link.

60% of the time it works every time