The swell and shrink factors are based on the material in its original state. If you combine the two factors you get a factor (Spike's compaction factor) which will convert loose state volume to compacted volume of the material. You can use this factor to estimate the amount of material you need to bring in for a certain area that needs to be compacted.
Spike's Compaction Factor can also be used to estimate the amount of material you need to purchase for an area that needs to be filled and compacted. For instance, you need to place a 6" layer of gravel inside a foundation. Your calculation of the area for a 20' x 20' wide with a depth of 6" would give you a volume needed of 20 * 20 * .5 = 200 cubic feet.From the first example, the compaction factor = 1.237 based on 15% swell and -7% shrink for this material.