[zenith]

The longer you are in your gang, the more protection you can have stored up. If you were in there for 1 day and used it, you'd get 100% and the excess lost. When you are in a gang for a long time, you receive the same amount when using the option... but you aren't at full capacity because you can store up more.

For example (the numbers are not the formula, they are just for example purposes)...

Jim uses gang back-up for 10 points and gets 10 rounds of backup.

If Jim was in his gang for 1 day, he could store 5 rounds. So he gets 5, loses the rest, and is listed at 100%.

If Jim was in his gang for 100 days, he could store 20 round. So he gets 10 and is listed at 50%.