Three ways to find Zone 2
Heart-rate reserve (Karvonen)
Uses both resting and max heart rate: resting HR + 60-70% of (max HR - resting HR). It adjusts for fitness, so it's the default when you enter a resting HR.
Percent of max HR
60-70% of your max heart rate. Simple, but it ignores resting HR, so it tends to come out lower than the other two.
MAF (Maffetone)
180 minus your age as the ceiling, with the range running 10 beats below it.
About max heart rate
220 - age is only a rough estimate and can be off by 10 or more beats either way. If you know your real max from a hard test or race, type it in.
