My samples copper levels:
Miles on truck (actual miles on oil)
3,520 mi (3,520 mi on oil) - 52ppm
6,351 mi (1,624 mi on oil) - 13ppm
9,323 mi (4,596 mi on oil) - 24ppm
14,243 mi (4,920 mi on oil) - 20ppm
18,811 mi (4,509 mi on oil) - 8ppm
Those are samples were taken at the time I got the "oil change required" message. I did not actually change the oil until the 5,000 mile mark, so the second reading is low due to less miles on the oil at the time of sampling.
Regardless, your sample reading is high for a second oil change. From what I've read, copper levels can vary widely due to multiple sources within the engine and cooling system, so '25' may be an average, but let's say the standard deviation of copper in a large group of samples is 67. This would mean that statistically you are within two standard deviations of normal and therefore should not be "sky is falling" concerned.
At this point, you should just monitor through continued regular sampling. I'd agree that 5000 miles seems to be a good change interval on the 6. 7L.