Your light settings will change spectrum with each progressive stage. For stage 1, 2 and 3 your lights will be on for 20 hours a day. Your young plant will sleep for only 4 hours during these stages.
Once stage 4 (transition) arrives, the lights spectrum and photoperiod both change drastically. You will now see more red in your spectrum, and notice your lights are now on for 12 hours a day and the plant sleeps for the other 12. This is the beginning of the flowering stages 4, 5 and 6.
I've selected the Generic - Hybrid recipe as an example, which has 3 vegetative stages and 3 flowering stages. We have just entered the early germination stage and our little plant is 11 days old. It has another month or 27 days left to grow before we flip to 12 hours of darkness each day and start producing flowers. Our goal is to have the plant as tall as the 2nd intake fan on the back wall when it moves into stage 4.
If you top or fim your plant, add a week to stage 2 or stage 3. You will stress your plant a bit and it needs time to recover and continue it's growth.