Let's try to make it easier for you to understand. In the fourth place of decimals we have the number 9 and next to it 6. Anything above 5 in the 5th decimal place means we need to adjust the 4th decimal place to round up. That means we add 1 to the 9, but because adding 1 makes 10, we have to carry over to the 3rd decimal place making 50. The final result is 12.0950. We can't write 12.095 because we want to show that we've gone the whole hog and produced an answer correct to 4 decimal places, not 3. The final zero confirms accuracy to 4 decimal places.