Much has been written about this issue both in this forum and elsewhere. Generally, if the crystal manufacturer says load cap 32pF then that is what you should use. Note that the cpu has capacitance on it's pin (see datasheet on actual cpu)) so that should be subtracted from the specified crystal capacitance to get the number of pF you need to add in the form of a capacitor. In many instances the actual value is not too critical so don't get too uptight about being precise about it. Varying the load capacitance shifts the crystal frequency slightly which in many cases is not a problem. If you're using the crystal for a real time clock then the actual frequency has an impact on the timekeeping - note there is also temperature and aging effects that come into play. Do a search on the web on this subject and you'll find a lot of information on crystals that should better answer your question.