Two thoughts about "uncertainty" in measurements:
1. To understand the uncertainty in the operator's ability to collect the data (i.e. variability in measurement) you would measure the length of the same wire ten times, and determine the standard deviation in the measurements. But that's not the data they gave you, so that's not what they're looking for.
2. If data is reported to the nearest 0.1m, the true length could be anywhere within 0.05 meters of the reported length. Hence the total uncertainty is 0.1m. For example a wire reported as being 4.3m in length might actually be anywhere from 4.25 to 4.35 meters in length. Stated another way: two wires both reported as being 4.3m long may actually differ in length by as much as 0.1 meters. I think that's the level of uncertainty that they're looking for.