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By changing the corresponding min/max values, you can remap the gradient on the volumetric cloud, to make parts of it appear more prominently, or even make the gradient start to repeat. For example, if you set the max value to 0.2 instead of 0.884 in this case, the entire gradient will be mapped to parts of the grid that fall within the range 0.0 - 0.2. In areas of the grid that exceed that range, the grid will be repeated (if texture tiling is turned on), this time between the range 0.2-0.4, then repeated again between 0.4 -0.6, and again between 0.6 - 0.8. So we would have approximately 4 repeats in this case. On the other hand, if you set a max value double of what is stored in the grid, the actual max value of the grid will be "reached" much sooner and only the left half of the gradient will be visible on the volumetric. Finally, if you have texture tiling turned off and you use a smaller max value than the grid holds, when areas in the grid have higher max values then you've specified, the texture won't be repeated and instead it's the materials Reflectance 0 color that will show. The following four renders demonstrate using different max values and tiling set to on and off:
In the upper Upper left render, the "true" max value of the grid was used and so the gradient was mapped in the most accurate, or predictable way. In the upper right renderUpper right, the gradient is repeated several times. Lower left, since the max value used is double compared to what is actually stored in the grid, only half of the gradient is mapped to it. Lower right render, tiling was off, and the reflectance 0 color was white - the gradient is only mapped to parts of the grid whose range is 0.0 - 0.2, and in parts with higher ranges, the reflectance 0 color becomes visible.