Jose,
The 90/270 has a tremendous advantage when making turns and remembering
where to turn.

The system is called the 'sum of the digits'

Take any number of the heading indicator and add all three of
its digits and keep adding until you get a single digit.

Example #1 030 = 3
Example #2 290 = 11 = 2

The sum of the digits every 90-degrees all the way around the dial will
equal 3 or 2 in both cases. It works for every number on both
the 90-degree numbers and 45-degree numbers.
Example #1
030 = 3; 120 = 3; 210= 3; 300 = 3
Example #2
290 = 11 = 2; 020= 2; 110 = 2; 200= 2

Works all the time everytime.
Gene