When solving an addition problem involving numbers with different levels of precision, the result should be rounded to the least precise decimal place among the numbers involved.
Consider the numbers:
1. 6.339 m: This number has three decimal places.
2. 0.170 m: This number also has three decimal places.
3. 30.4 m: This number has one decimal place.
The number 30.4 m is the least precise number with only one decimal place. Therefore, the sum of these numbers should be rounded to one decimal place as well.
The level of precision in this case corresponds to the least precise decimal place, which is one decimal place or 0.1 meters.
Therefore, the level of precision for this addition problem is:
[tex]\[ \boxed{0.1 \text{ m}} \][/tex]
