A friend of mine gave me a Brower 845 incubator. I am reading the manual as I am getting prepared to hatch my first cluth of eggs. Everything makes sense except for one section which refers to cooling the eggs. It says that for the 1st week, no cooling is necessary. But each day after the 1st week the eggs should be cooled for about 10-15 minutes, increasing the time several minutes each day until the end of day 18. What does that mean exactly, and how do I do it?