+Ambient Light measurement is not necessary when profiling your monitor
When using an i1Display2 or i1Spectrophotometer, i1Match will give you the option to take a measurement of ambient light conditions. While this is useful information to know, it is not necessary to do when profiling your monitor, and the results will not affect the monitor profile you create.
Ambient light (or the light conditions in the room around the monitor) can vary considerably in terms of color of the light and the intensity of the light. In a perfect world, we would either eliminate all room light or make sure that the room light was set to a known standard (we recommend 5000K as this standard light condition).
However, this is not always possible or convenient, due to room lighting conditions and types of lamps used in the average work area. Unless you have a really unusual lighting condition, or have a direct shadow or beam of light hitting the monitor and causing glare, you need not perform this measurement.
If you do choose to run the ambient light measurement, you may find that your work area has a color temperature other than 5000K, the only way to change this would be to buy different lights for your room lighting fixtures.
Ambient light temperature is very important when judging a print result however, and this is why professionals use a light booth set to 5000K, or walk to a window to judge a print result for accurate color.