I had purchased a canister of re-charge that had a gauge on it and a co-worker re-filled it this last summer (it didn't need as much re-charging as I thought I just wanted it topped off for summer last year) and he used about half of the bottle. I used it all last summer, it worked fine, and most of this summer it worked fine until that happened.

When I plug in the re-charge canister and check the gauge can someone tell me what the pressure should be at or how "full" the system should be?