Changing dive time based on temperature?

One of the NAUI dive table rules is to "Use the next greater dive time if your dive is particularly cold or strenuous." What exactly does this mean? What is "particularly cold?"

Thanks.

All the tables are basically a guide. You don't suddenly go from being un-bent if you make a direct ascent to the surface to being bent the next minute. But we know that some things retard off gassing, like old, cold, exertion, etc. For some people, sometimes, and sometimes not. Heck, it's all just a big WAG anyway, because every dive and every diver's body is different day to day (see my quote in my signature line ).

Bottom line, the move to the next greater time is just a way of adding some conservatism if conditions are such that you are not off-gas at maximum efficiency.