It's hard to tell from the picture. I would expect clutch pads to last longer than 28,000 miles but I guess it depends on how you ride it. A lot of stop and go will wear it out faster.
You need to measure how thick it is and find out what the minimum thickness is supposed to be. If it's below the minimum thickness then replace it. If it's above that but close then you need to replace it soon. Once it wears too much you will start getting metal to metal contact and ruin your clutch bell.