In order for you to take advantage of the Water Guide you need to know some things about your system.
The main one is, how long does it take my system to put down a specific amount of water? The easiest way to answer this is to put out a few old cat food or tuna cans out on your lawn. Make sure you get information from each zone or area. Run your system for a known amout of time like 30 minutes. Measure the amount of water in the can and then figure out how long your system would take to apply 25mm/ 1" of water.
Your system, if designed properly, should have everywhere covered by 2 heads so if those heads are on different zones make sure you run both zones for 30 minutes to get an accurate reading.
If you water manually you do the same thing. Run the sprinkler for a set time with 2 or 3 cans underneath and do the math.
Once you know how long for 25mm/1", go and set the zone times for that duration and, until July, to water once per week. Then using the Watering Guide numbers and your "season adjust" or "water budget" setting to the percentage given in the Water Guide.
If you water manually adjust your time accordingly. If it takes 1 hr usually and the Water Guide says 80% only do 8/10ths of an hour or 48 minutes.