When its at 100% of what the adapter will provide, why not just have the computer show at 100% battery life?
It is not an indication of what the adapter will provide.
When your battery is charged to 100% it will show 100%. If it is charged to 99% it shows 99%. Etc.
... The battery may appear to stop charging between 93 percent and 99 percent.
Note: PowerPC-based computers may stop charging between 95 and 99 percent; Intel-based computers may stop charging between 93 and 99 percent.
This is normal. The batteries used in these computers are designed to avoid short discharge/charge cycles in order to prolong the overall life of the battery.